28 results on '"Luporini, Pierangelo"'
Search Results
2. Functional chimeric genes in ciliates: An instructive case from Euplotes raikovi.
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Ricci, Francesca, Luporini, Pierangelo, Alimenti, Claudio, and Vallesi, Adriana
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GENES , *GENE families , *NUCLEOTIDE sequence , *PROTEIN synthesis , *RNA splicing , *NUCLEOLUS , *GENETIC recombination - Abstract
• Chimeric genes are generated by ciliates during the macronuclear development. • In Euplotes raikovi , a pheromone-coding gene, mac-er-1 , coexists with a chimeric copy, mac-er-1*. • mac-er-1* originates from the mac-er-1 assembly with an extraneous sequence. • mac-er-1* is functional and practically duplicates the mac-er-1 activity. In ciliates, with every sexual event the transcriptionally active genes of the sub-chromosomic somatic genome that resides in the cell macronucleus are lost. They are de novo assembled starting from ' M acronuclear D estined S equences' that arise from the fragmentation of transcriptionally silent DNA sequences of the germline chromosomic genome enclosed in the cell micronucleus. The RNA-mediated epigenetic mechanism that drives the assembly of these sequences is subject to errors which result in the formation of chimeric genes. Studying a gene family that in Euplotes raikovi controls the synthesis of protein signal pheromones responsible for a self/not-self recognition mechanism, we identified the chimeric structure of an 851-bp macronuclear gene previously known to specify soluble and membrane-bound pheromone molecules through an intron-splicing mechanism. This chimeric gene, designated mac-er-1* , conserved the native pheromone-gene structure throughout its coding and 3′ regions. Instead, its 5′ region is completely unrelated to the pheromone gene structure at the level of a 360-bp sequence, which derives from the assembly with a MDS destined to compound a 2417-bp gene encoding a 696-amino acid protein with unknown function. This mac-er-1* gene characterization provides further evidence that ciliates rely on functional chimeric genes that originate in non-programmed phenomena of somatic MDS recombination to increase the species genetic variability independently of gene reshuffling phenomena of the germline genome. [ABSTRACT FROM AUTHOR]
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- 2021
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3. Cell aging-induced methionine oxidation causes an autocrine to paracrine shift of the pheromone activity in the protozoan ciliate, Euplotes raikovi
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Alimenti, Claudio, Vallesi, Adriana, Luporini, Pierangelo, Buonanno, Federico, and Ortenzi, Claudio
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METHIONINE , *OXIDATION , *PARACRINE mechanisms , *ENZYME activation , *CILIATA , *CELL growth , *AUTOCRINE mechanisms , *CHEMICAL synthesis , *ENZYMES - Abstract
Abstract: Ciliates of the genus Euplotes rely on the autocrine (self) and paracrine (non-self) activities of their water-borne protein pheromones to control the two fundamental phenomena of their life cycle, i.e. vegetative (mitotic) growth and sex manifested as cell union in mating pairs. We observed that cell aging determines the synthesis of increasing concentrations of pheromones that are oxidized at the level of methionine residues which are more exposed on the molecular surface. The oxidized form of the E. raikovi pheromone Er-1 was purified and its interactions with its source cells were shown no longer to be of autocrine type directed to promote cell growth, but changed to interactions of the paracrine type directed to induce cell unions in mating pairs of the selfing type (i.e. involving genetically identical cells). These pairs generate viable offspring, like pairs formed between genetically different cells. It was therefore concluded that aging cells may paradoxically gain beneficial effects from the synthesis of oxidized forms of their pheromones. By undergoing mating in response to the interactions with these forms, they can re-initiate a new life cycle and, in fact, rejuvenate. [Copyright &y& Elsevier]
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- 2012
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4. Ancient Immunity. Phylogenetic Emergence of Recognition-Defense Mechanisms.
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Ballarin, Loriano, Cammarata, Matteo, and Luporini, Pierangelo
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ANIMAL diversity , *IMMUNITY , *POMACEA canaliculata , *COLONIAL animals (Marine invertebrates) , *ANIMAL defenses - Abstract
Indeed, invertebrates represent the overwhelming majority of animal biodiversity and this simple assumption can explain the growing interest of the scientific community towards various aspects of their biology. 32560112 4 Auguste M., Balbi T., Ciacci C., Canesi L. Conservation of cell communication systems in invertebrate host-defence mechanisms: Possible role in immunity and disease. Its amino acid sequence is well conserved in vertebrates and invertebrates: this suggests its involvement also in invertebrate inflammatory responses. [Extracted from the article]
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- 2021
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5. The Sub‐Chromosomic Macronuclear Pheromone Genes of the Ciliate Euplotes raikovi: Comparative Structural Analysis and Insights into the Mechanism of Expression.
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Ricci, Francesca, Candelori, Annalisa, Brandi, Anna, Alimenti, Claudio, Luporini, Pierangelo, and Vallesi, Adriana
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PHEROMONES , *CILIATA , *EUPLOTES , *GENE expression , *GENETIC transcription - Abstract
In Euplotes raikovi, we have determined the full‐length sequences of a family of macronuclear genes that are the transcriptionally active versions of codominant alleles inherited at the mating‐type (mat) locus of the micronuclear genome, and encode cell type‐distinctive signaling pheromones. These genes include a 225–231‐bp coding region flanked by a conserved 544‐bp 5′‐leader region and a more variable 3′‐trailer region. Two transcription initiation start sites and two polyadenylation sites associated with nonconventional signals cooperate with a splicing phenomenon of a 326‐bp intron residing in the 5′‐leader region in the generation of multiple transcripts from the same gene. In two of them, the synthesis of functional products depends on the reassignment to a sense codon, or readthrough of a strictly conserved leaky UAG stop codon. That this reassignment may take place is suggested by the position this codon occupies in the transcripts, close to the transcript extremity and far from the poly(A) tail. In such a case, one product is a 69‐amino acid protein in search of function and the second product is a 126‐amino acid protein that represents a membrane‐bound pheromone isoform candidate to function as a cell type‐specific binding site (receptor) of the soluble pheromones. [ABSTRACT FROM AUTHOR]
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- 2019
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6. A New Species of the γ-Proteobacterium Francisella, F. adeliensis Sp. Nov., Endocytobiont in an Antarctic Marine Ciliate and Potential Evolutionary Forerunner of Pathogenic Species.
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Vallesi, Adriana, Sjödin, Andreas, Petrelli, Dezemona, Luporini, Pierangelo, Taddei, Anna Rita, Thelaus, Johanna, Öhrman, Caroline, Nilsson, Elin, Di Giuseppe, Graziano, Gutiérrez, Gabriel, and Villalobo, Eduardo
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PROTEOBACTERIA , *PATHOGENIC microorganisms , *FRANCISELLA , *CARBON dioxide , *BIOSYNTHESIS - Abstract
The study of the draft genome of an Antarctic marine ciliate, Euplotes petzi, revealed foreign sequences of bacterial origin belonging to the γ-proteobacterium Francisella that includes pathogenic and environmental species. TEM and FISH analyses confirmed the presence of a Francisella endocytobiont in E. petzi. This endocytobiont was isolated and found to be a new species, named F. adeliensis sp. nov.. F. adeliensis grows well at wide ranges of temperature, salinity, and carbon dioxide concentrations implying that it may colonize new organisms living in deeply diversified habitats. The F. adeliensis genome includes the igl and pdp gene sets (pdpC and pdpE excepted) of the Francisella pathogenicity island needed for intracellular growth. Consistently with an F. adeliensis ancient symbiotic lifestyle, it also contains a single insertion-sequence element. Instead, it lacks genes for the biosynthesis of essential amino acids such as cysteine, lysine, methionine, and tyrosine. In a genome-based phylogenetic tree, F. adeliensis forms a new early branching clade, basal to the evolution of pathogenic species. The correlations of this clade with the other clades raise doubts about a genuine free-living nature of the environmental Francisella species isolated from natural and man-made environments, and suggest to look at F. adeliensis as a pioneer in the Francisella colonization of eukaryotic organisms. [ABSTRACT FROM AUTHOR]
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- 2019
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7. The Anti-Oxidant Defense System of the Marine Polar Ciliate Euplotes nobilii: Characterization of the MsrB Gene Family.
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Ricci, Francesca, Lauro, Federico M., Grzymski, Joseph J., Read, Robert, Bakiu, Rigers, Santovito, Gianfranco, Luporini, Pierangelo, and Vallesi, Adriana
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CILIATA , *EUPLOTES , *PROTOZOAN genes , *ANTIOXIDANTS , *METHIONINE sulfoxide reductase , *PHYSIOLOGICAL effects of ultraviolet radiation - Abstract
Organisms living in polar waters must cope with an extremely stressful environment dominated by freezing temperatures, high oxygen concentrations and UV radiation. To shed light on the genetic mechanisms on which the polar marine ciliate, Euplotes nobilii, relies to effectively cope with the oxidative stress, attention was focused on methionine sulfoxide reductases which repair proteins with oxidized methionines. A family of four structurally distinct MsrB genes, encoding enzymes specific for the reduction of the methionine-sulfoxide R-forms, were identified from a draft of the E. nobilii transcriptionally active (macronuclear) genome. The En-MsrB genes are constitutively expressed to synthesize proteins markedly different in amino acid sequence, number of CXXC motifs for zinc-ion binding, and presence/absence of a cysteine residue specific for the mechanism of enzyme regeneration. The En-MsrB proteins take different localizations in the nucleus, mitochondria, cytosol and endoplasmic reticulum, ensuring a pervasive protection of all the major subcellular compartments from the oxidative damage. These observations have suggested to regard the En-MsrB gene activity as playing a central role in the genetic mechanism that enables E. nobilii and ciliates in general to live in the polar environment. [ABSTRACT FROM AUTHOR]
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- 2017
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8. Bioactive molecules from ciliates: Structure, activity, and applicative potential.
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Alimenti, Claudio, Buonanno, Federico, Di Giuseppe, Graziano, Guella, Graziano, Luporini, Pierangelo, Ortenzi, Claudio, and Vallesi, Adriana
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COLONIZATION (Ecology) , *MOLECULES , *PREDATION , *CILIATA , *TERPENES - Abstract
Ciliates are a rich source of molecules synthesized to socialize, compete ecologically, and interact with prey and predators. Their isolation from laboratory cultures is often straightforward, permitting the study of their mechanisms of action and their assessment for applied research. This review focuses on three classes of these bioactive molecules: (i) water‐borne, cysteine‐rich proteins that are used as signaling pheromones in self/nonself recognition phenomena; (ii) cell membrane‐associated lipophilic terpenoids that are used in interspecies competitions for habitat colonization; (iii) cortical granule‐associated molecules of various chemical nature that primarily serve offence/defense functions. [ABSTRACT FROM AUTHOR]
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- 2022
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9. Genetic relationships in bipolar species of the protist ciliate, Euplotes.
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Di Giuseppe, Graziano, Dini, Fernando, Vallesi, Adriana, and Luporini, Pierangelo
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EUPLOTES , *PROTOZOA genetics , *SPECIES distribution , *RIBOSOMAL RNA , *CROSS-fertilization (Biology) , *CLASSIFICATION of protozoa , *MORPHOLOGY of protozoa - Abstract
Protists thrive in polar oceans, where they represent a major driving force for globally important biogeochemical cycles and a key food-web component. Their biogeography is frequently associated to bipolar patterns of distribution. Although conceptually well supported by apparently unrestricted migration rates, the experimental certification of these patterns copes with the protist paucity of morphological characters with taxonomic value and difficulties in applying conventional species concepts. We studied three marine species of the ciliate Euplotes, E. euryhalinus, E. nobilii, and E. petzi, for their bipolar distribution by comparing the SSU-rRNA gene sequences and mating interactions of Antarctic, Patagonian, and Arctic strains. Each species was analogously found not to carry significantly varied SSU-rRNA gene sequences, implying a common occurrence of trans-equatorial genetic mixing. However, mating analyses revealed significant inter-species differences. Scarce Antarctic × Arctic strain mating compatibility distinguished E. petzi from E. euryhalinus and E. nobilii, in which mating pairs between Antarctic and Arctic strains were successfully induced. Yet, E. nobilii was the only one of the two species to show cross-fertilizing and fertile mating pairs. Taking the biological concept of species as discriminatory, it was thus concluded that only E. nobilii warrants the definition of genuine bipolar species. [ABSTRACT FROM AUTHOR]
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- 2015
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10. Evidence for methionine-sulfoxide-reductase gene transfer from Alphaproteobacteria to the transcriptionally active (macro)nucleus of the ciliate, Euplotes raikovi
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Dobri, Nicoleta, Candelori, Annalisa, Ricci, Francesca, Luporini, Pierangelo, and Vallesi, Adriana
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Background: Deleterious phenomena of protein oxidation affect every aerobic organism and methionine residues are their elective targets. The reduction of methionine sulfoxides back to methionines is catalyzed by methionine-sulfoxide reductases (Msrs), enzymes which are particularly active in microorganisms because of their unique nature of individual cells directly exposed to environmental oxidation. Results: From the transcriptionally active somatic genome of a common free-living marine protist ciliate, Euplotes raikovi, we cloned multiple gene isoforms encoding Msr of type A (MsrA) committed to repair methionine-S-sulfoxides. One of these isoforms, in addition to including a MsrA-specific nucleotide sequence, included also a sequence specific for a Msr of type B (MsrB) committed to repair methionine-R-sulfoxides. Analyzed for its structural relationships with MsrA and MsrB coding sequences of other organisms, the coding region of this gene (named msrAB) showed much more significant relationships with Msr gene coding sequences of Rhodobacterales and Rhizobiales (Alphaproteobacteria), than of other eukaryotic organisms. Conclusions: Based on the fact that the msrAB gene is delimited by Euplotes-specific regulatory 5′ and 3′ regions and telomeric C4A4/G4T4 repeats, it was concluded that E. raikovi inherited the coding region of this gene through a phenomenon of horizontal gene transfer from species of Alphaproteobacteria with which it coexists in nature and on which it likely feeds. [ABSTRACT FROM AUTHOR]
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- 2014
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11. Evidence for Gene Duplication and Allelic Codominance (not Hierarchical Dominance) at the Mating-Type Locus of the Ciliate, Euplotes crassus.
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Vallesi, Adriana, Alimenti, Claudio, Federici, Sergio, Di Giuseppe, Graziano, Dini, Fernando, Guella, Graziano, and Luporini, Pierangelo
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ALLELES , *CHROMOSOME duplication , *EUPLOTES , *LOCUS (Genetics) , *INFERENCE (Logic) - Abstract
The high-multiple mating system of Euplotes crassus is known to be controlled by multiple alleles segregating at a single locus and manifesting relationships of hierarchical dominance, so that heterozygous cells would produce a single mating-type substance (pheromone). In strain L-2D, now known to be homozygous at the mating-type locus, we previously identified two pheromones (E c-α and E c-1) characterized by significant variations in their amino acid sequences and structure of their macronuclear coding genes. In this study, pheromones and macronuclear coding genes have been analyzed in strain POR-73 characterized by a heterozygous genotype and strong mating compatibility with L-2D strain. It was found that POR-73 cells contain three distinct pheromone coding genes and, accordingly, secrete three distinct pheromones. One pheromone revealed structural identity in amino acid sequence and macronuclear coding gene to the E c-α pheromone of L-2D cells. The other two pheromones were shown to be new and were designated E c-2 and E c-3 to denote their structural homology with the E c-1 pheromone of L-2D cells. We interpreted these results as evidence of a phenomenon of gene duplication at the E. crassus mating-type locus, and lack of hierarchical dominance in the expression of the macronuclear pheromone genes in cells with heterozygous genotypes. [ABSTRACT FROM AUTHOR]
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- 2014
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12. Phylogeographical pattern of Euplotes nobilii, a protist ciliate with a bipolar biogeographical distribution.
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Di Giuseppe, Graziano, Barbieri, Michele, Vallesi, Adriana, Luporini, Pierangelo, and Dini, Fernando
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PHYLOGEOGRAPHY , *EUPLOTES , *RIBOSOMAL RNA genetics , *BIOGEOGRAPHY , *MITOCHONDRIAL RNA , *PROTISTA - Abstract
Nuclear (18S and ITS) and mitochondrial (16S) ribosomal RNA gene sequences were determined from genetically distinct wild-type strains of Antarctic (nine strains), Fuegian (four strains), Greenland (nine strains) and Svalbard (three strains) populations of the marine ciliate, Euplotes nobilii, and analysed for their nucleotide polymorphisms. A close genetic homogeneity was found within and between the Antarctic and Fuegian populations, while more significant levels of genetic differentiation were detected within and between the two Arctic populations, as well as between these populations and the Antarctic/Fuegian ones. The phylogeographical pattern that was derived from these data indicates that gene flow is not limited among Arctic populations; it equally connects the Arctic and Antarctic populations either directly, or through the Fuegian population. This indication reinforces previous evidence from laboratory assays of mating interactions between some of the strains analysed in this work that Southern and Northern polar populations of E. nobilii belong to a unique, panmictic population that substantially share the same gene pool. [ABSTRACT FROM AUTHOR]
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- 2013
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13. Thermodynamic Stability of Psychrophilic and Mesophilic Pheromones of the Protozoan Ciliate Euplotes.
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Geralt, Michael, Alimenti, Claudio, Vallesi, Adriana, Luporini, Pierangelo, and Wüthrich, Kurt
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PHEROMONES , *EUPLOTES , *AQUEOUS solutions , *CIRCULAR dichroism , *NUCLEAR magnetic resonance - Abstract
Three psychrophilic protein pheromones (En-1, En-2 and En-6) from the polar ciliate, Euplotes nobilii, and six mesophilic pheromones (Er-1, Er-2, Er-10, Er-11, Er-22 and Er-23) from the temperate-water sister species, Euplotes raikovi, were studied in aqueous solution for their thermal unfolding and refolding based on the temperature dependence of their circular dichroism (CD) spectra. The three psychrophilic proteins showed thermal unfolding with mid points in the temperature range 55??70 °C. In contrast, no unfolding was observed for any of the six mesophilic proteins and their regular secondary structures were maintained up to 95 °C. Possible causes of these differences are discussed based on comparisons of the NMR structures of the nine proteins. [ABSTRACT FROM AUTHOR]
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- 2013
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14. Methionine sulfoxide reduction in ciliates: Characterization of the ready-to-use methionine sulfoxide-R-reductase genes in Euplotes
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Dobri, Nicoleta, Oumarou, Eugenie Emilie Ngueng, Alimenti, Claudio, Ortenzi, Claudio, Luporini, Pierangelo, and Vallesi, Adriana
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METHIONINE sulfoxide reductase , *CILIATA , *CELLULAR aging , *OXIDATIVE stress , *SELENOCYSTEINE , *POLYMERASE chain reaction - Abstract
Abstract: Genes encoding the enzyme methionine sulfoxide reductase type B, specific to the reduction of the oxidized methionine-R form, were characterized from the expressed (macronuclear) genome of two ecologically separate marine species of Euplotes, i.e. temperate water E. raikovi and polar water E. nobilii. Both species were found to contain a single msrB gene with a very simple structural organization encoding a protein of 127 (E. raikovi) or 126 (E. nobilii) amino acid residues that belongs to the group of zinc-containing enzymes. Both msrB genes are constitutively expressed, suggesting that the MsrB enzyme plays an essential role in repairing oxidative damages that appear to be primarily caused by physiological cell aging in E. raikovi and by interactions with an O2 saturated environment in E. nobilii. [Copyright &y& Elsevier]
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- 2013
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15. Isolation and Structural Characterization of Two Water-Borne Pheromones from Euplotes crassus, a Ciliate Commonly Known to Carry Membrane-Bound Pheromones.
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ALIMENTI, CLAUDIO, VALLESI, ADRIANA, FEDERICI, SERGIO, DI GIUSEPPE, GRAZIANO, FERNANDO, DINI, CARRATORE, VITALE, and LUPORINI, PIERANGELO
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EUPLOTES , *CILIATA , *PHEROMONES , *AMINO acid sequence , *LOCUS (Genetics) , *GENETIC transcription , *GENOMES - Abstract
Ciliates comprise species synthesizing water-diffusible mating type factors or pheromones and species synthesizing insoluble, cell membrane-bound pheromones. Euplotes crassus has traditionally been placed in the latter group. In contrast with this notion, we found that E. crassus is a constitutive pheromone-secreting ciliate, like other Euplotes species. From cell-free filtrate preparations of the E. crassus strain L-2D, we isolated two distinct pheromones, designated as E c-α and E c-1, and determined their complete amino acid sequences by combined chemical and genetic approaches. The E c-α pheromone sequence extends for 56 amino acid residues with six cysteines and shows a molecular mass of 6,183 Da, while the E c-1 pheromone sequence extends for 45 amino acid residues with 10 cysteines and shows a molecular mass of 4,840 Da. Marked structural differences distinguish the full-length E c-α and E c-1 coding sequences, which have been cloned and characterized from the transcriptionally active macronuclear genome. They were taken as clear indication that the E c-α and E c-1 pheromones are specified by genes that are not allelic, but likely derived from a duplicated genetic locus of the transcriptionally silent micronuclear genome. [ABSTRACT FROM AUTHOR]
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- 2011
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16. Antarctic and Arctic populations of the ciliate Euplotes nobilii show common pheromone- mediated cell-cell signaling and cross-mating.
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Di Giuseppe, Graziano, Erra, Fabrizio, Dini, Fernando, Alimenti, Claudio, Vallesi, Adriana, Pedrini, Bill, Wüthrich, Kurt, and Luporini, Pierangelo
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CILIATA , *EUPLOTES , *PHEROMONES , *CELL communication , *BIOLOGICAL classification - Abstract
Wild-type strains of the protozoan ciliate Euplotes collected from different locations on the coasts of Antarctica, Tierra del Fuego and the Arctic were taxonomically identified as the morpho-species Euplotes nobiiii, based on morphometric and phylogenetic analyses. Subsequent studies of their sexual interactions revealed that mating combinations of Antarctic and Arctic strains form stable pairs of conjugant cells. These conjugant pairs were isolated and shown to complete mutual gene exchange and cross-fertilization. The biological significance of this finding was further substantiated by demonstrating that close homology exists among the three- dimensional structures determined by NMR of the water-borne signaling pheromones that are constitutively secreted into the extracellular space by these interbreeding strains, in which these molecules trigger the switch between the growth stage and the sexual stage of the life cycle. The fact that Antarctic and Arctic E. nobilll populations share the same gene pool and belong to the same biological species provides new support to the biogeographic model of global distribution of eukaryotic microorganisms, which had so far been based exclusively on studies of morphological and phylogenetic taxonomy. [ABSTRACT FROM AUTHOR]
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- 2011
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17. Molecular cold-adaptation: Comparative analysis of two homologous families of psychrophilic and mesophilic signal proteins of the protozoan ciliate, Euplotes.
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Alimenti, Claudio, Vallesi, Adriana, Pedrini, Bill, Wüthrich, Kurt, and Luporini, Pierangelo
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COLD (Temperature) , *MOLECULES , *PROTEINS , *EUPLOTES , *AMINO acids - Abstract
Unique opportunities are provided by phylogenetically closely related organisms thriving in stably cold, or temperate milieus to study adaptive modifications of structurally homologous molecules. These modifications are of keen interest in basic science as well as in biotechnology. This review highlights structural and functional specificities that differentiate two homologous families of psychrophilic and mesophilic water-borne proteins (designated as pheromones) that signal mitotic growth and sexual mating in two marine species of the protozoan ciliate Euplotes, i.e., E. nobilii, which is distributed in Antarctic and Arctic waters, and E. raikovi, which inhabits temperate waters. The two protein families show strict conservation of a common three-helix bundle in a compact core of the molecular structure, which provides long-lasting integrity and biological activity to these molecules in their natural environment. In the psychrophilic pheromone family, cold-adaptation appears to have been achieved by superimposing an integrated complex of structural modifications on this conserved scaffold. Functionally most relevant appear to be extensions of polypeptide segments devoid of regular secondary structures, a specific distribution of polar and hydrophobic amino acids, the presence of solvent-exposed clusters of negatively charged amino acid side chains, and a unique role of aromatic residues in anchoring the molecular architecture. Due to these modifications, the psychrophilic pheromones are an example of an elegant combination of high stability of the three-dimensional structures with sufficient structural plasticity for efficient functioning at their physiologically low temperatures. © 2009 IUBMB IUBMB Life 61(8): 838–845, 2009 [ABSTRACT FROM AUTHOR]
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- 2009
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18. Crystal structure of the pheromone Er-13 from the ciliate Euplotes raikovi, with implications for a protein–protein association model in pheromone/receptor interactions.
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Pedrini, Bill, Finke, Aaron D., Marsh, May, Luporini, Pierangelo, Vallesi, Adriana, and Alimenti, Claudio
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CRYSTAL structure , *CELL receptors , *PHEROMONES , *PROTEIN-protein interactions - Abstract
[Display omitted] • The crystal structure of E. raikovi pheromone E r -13 was determined at 1.36 Å of resolution. • E r -13 molecules associate cooperatively into linear chains taking opposite orientations. • Helix-3 is the key functional domain of the three-helical pheromone structure. • The E r -13 crystal structure compared with the known E r -1 structure provides insights to seek into pheromone/receptor interactions. In the ciliate Euplotes raikovi , water-borne protein pheromones promote the vegetative cell growth and mating by competitively binding as autocrine and heterologous signals to putative cell receptors represented by membrane-bound pheromone isoforms. A previously determined crystal structure of pheromone E r -1 supported a pheromone/receptor binding model in which strong protein–protein interactions result from the cooperative utilization of two distinct types of contact interfaces that arrange molecules into linear chains, and these into two-dimensional layers. We have now determined the crystal structure of a new pheromone, E r -13, isolated from cultures that are strongly mating reactive with cultures source of pheromone E r -1. The comparison between the E r -1 and E r -13 crystal structures reinforces the fundamental of the cooperative model of pheromone/receptor binding, in that the molecules arrange into linear chains taking a rigorously alternate opposite orientation reflecting the presumed mutual orientation of pheromone and receptor molecules on the cell surface. In addition, the comparison provides two new lines of evidence for a univocal rationalization of observations on the different behaviour between the autocrine and heterologous pheromone/receptor complexes. (i) In the E r -13 crystal, chains do not form layers which thus appear to be an over-structure unique to the E r -1 crystal, not essential for the pheromone signalling mechanisms. (ii) In both crystal structures, the intra-chain interfaces are equally derived from burying amino-acid side-chains mostly residing on helix-3 of the three-helical pheromone fold. This helix is thus identified as the key structural motif underlying the pheromone activity, in line with its tight intra- and interspecific structural conservation. [ABSTRACT FROM AUTHOR]
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- 2022
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19. The water-borne protein signals (pheromones) of the Antarctic ciliated protozoan Euplotes nobilii: structure of the gene coding for the En-6 pheromone.
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La Terza, Antonietta, Dobri, Nicoleta, Alimenti, Claudio, Vallesi, Adriana, and Luporini, Pierangelo
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CILIATA , *EUPLOTES , *PHEROMONES , *MARINE microbial ecology , *VEGETATIVE propagation , *PROTEOLYTIC enzymes - Abstract
The marine Antarctic ciliate, Euplotes nobilii, secretes a family of water-borne signal proteins, denoted as pheromones, which control vegetative proliferation and mating in the cell. Based on the knowledge of the amino acid sequences of a set of these pheromones isolated from the culture supernatant of wild-type strains, we designed probes to identify their encoding genes in the cell somatic nucleus (macronucleus). The full-length gene of the pheromone En-6 was determined and found to contain an open-reading frame specific for the synthesis of the En-6 cytoplasmic precursor (pre-pro-En-6), which requires 2 proteolytic cleavages to remove the signal peptide (pre) and the prosegment before secretion of the mature protein. In contrast to the sequence variability that distinguishes the secreted pheromones, the pre- and pro-sequences appear to be tightly conserved and useful for the construction of probes to clone every other E. nobilii pheromone gene. Potential intron sequences in the coding region of the En-6 gene imply the synthesis of more En-6 isoforms. [ABSTRACT FROM AUTHOR]
- Published
- 2009
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20. Pheromone evolution in the protozoan ciliate, Euplotes: The ability to synthesize diffusible forms is ancestral and secondarily lost
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Vallesi, Adriana, Giuseppe, Graziano Di, Dini, Fernando, and Luporini, Pierangelo
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- 2008
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21. Cold-adaptation in Sea-water-borne Signal Proteins: Sequence and NMR Structure of the Pheromone En-6 from the Antarctic Ciliate Euplotes nobilii
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Pedrini, Bill, Placzek, William J., Koculi, Eda, Alimenti, Claudio, LaTerza, Antonietta, Luporini, Pierangelo, and Wüthrich, Kurt
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EUPLOTES , *PHEROMONES , *ANIMAL sexual behavior , *GROWTH factors - Abstract
Abstract: Ciliates of Euplotes species constitutively secrete pleiotropic protein pheromones, which are capable to function as prototypic autocrine growth factors as well as paracrine inducers of mating processes. This paper reports the amino acid sequence and the NMR structure of the pheromone En-6 isolated from the antarctic species Euplotes nobilii. The 63-residue En-6 polypeptide chain forms three α-helices in positions 18–25, 36–40 and 46–56, which are arranged in an up-down-up three-helix bundle forming the edges of a distorted trigonal pyramid. The base of the pyramid is covered by the N-terminal heptadecapeptide segment, which includes a 310-turn of residues 3–6. This topology is covalently anchored by four long-range disulfide bonds. Comparison with the smaller pheromones of E. raikovi, a closely related species living in temperate waters, shows that the two-pheromone families have the same three-helix bundle architecture. It then appears that cold-adaptation of the En proteins is primarily related to increased lengths of the chain-terminal peptide segments and the surface-exposed loops connecting the regular secondary structures, and to the presence of solvent-exposed clusters of negatively charged side-chains. [Copyright &y& Elsevier]
- Published
- 2007
- Full Text
- View/download PDF
22. Cold-adapted signal proteins: NMR structures of pheromones from the antarctic ciliate Euplotes nobilii.
- Author
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Placzek, William J., Etezady-Esfarjani, Touraj, Herrmann, Torsten, Pedrini, Bill, Peti, Wolfgang, Alimenti, Claudio, Luporini, Pierangelo, and Wüthrich, Kurt
- Subjects
- *
PHEROMONES , *PROTEINS , *EUPLOTES , *CILIATA , *BIOMOLECULES , *CELLS - Abstract
Cell type-specific signal proteins, known as pheromones, are synthesized by ciliated protozoa in association with their self/nonself mating-type systems, and are utilized to control the vegetative growth and mating stages of their life cycle. In species of the most ubiquitous ciliate, Euplotes, these pheromones form families of structurally homologous molecules, which are constitutively secreted into the extracellular environment, from where they can be isolated in sufficient amounts for chemical characterization. This paper describes the NMR structures of En-1 and En-2, which are members of the cold-adapted pheromone family produced by Euplotes nobilii, a species inhabiting the freezing coastal waters of Antarctica. The structures were determined with the proteins from the natural source, using homonuclear 1H NMR techniques in combination with automated NOESY peak picking and NOE assignment. En-1 and En-2 have highly homologous global folds, which consist of a central three-α-helix bundle with an up-down-up topology and a 310-helical turn near the N-terminus. This fold is stabilized by four disulfide bonds and the helices are connected by bulging loops. Apparent structural specificity resides in the variable C-terminal regions of the pheromones. The NMR structures of En-1 and En-2 provide novel insights into the cold-adaptive modifications that distinguish the E. nobilii pheromone family from the closely related E. raikovi pheromone family isolated from temperate waters. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
23. Cross-talk between the autocrine (mitogenic) pheromone loop of the ciliate euplotes raikovi and the intracellular cyclic AMP concentration
- Author
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Apone, Fabio, Vallesi, Adriana, Di Pretoro, Barbara, and Luporini, Pierangelo
- Subjects
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CELLULAR signal transduction , *AUTOCRINE mechanisms - Abstract
Cell type-specific protein signals, called pheromones, are constitutively secreted by Euplotes raikovi and bound back in autocrine fashion, with a positive effect on the vegetative (mitotic) cell growth. In cells growing suspended with their secreted pheromone, it was found that any interruption of this autocrine signaling loop was immediately followed by an effective enhancement of the basal intracellular cyclic AMP (cAMP) level. To establish a cause-effect relationship between these pheromone-induced variations in the cytoplasmic cAMP level and cell growth, cells ready to pass from a resting stage to a new growth cycle were conditioned either to incorporate a cAMP analog resistant to phosphodiesterase degradation, or to utilize cAMP released (following cell irradiation) from incorporated “caged” cAMP. Cells responded at every induced increase in their basal cAMP level by markedly decreasing their commitment to start a new growth cycle. It was deduced that the autocrine signaling of E. raikovi pheromones involves cAMP as inhibitor of its mitogenic activity. [Copyright &y& Elsevier]
- Published
- 2003
- Full Text
- View/download PDF
24. Structural characterization of En-1, a cold-adapted protein pheromone isolated from the Antarctic ciliate Euplotes nobilii
- Author
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Alimenti, Claudio, Ortenzi, Claudio, Carratore, Vito, and Luporini, Pierangelo
- Subjects
- *
PROTEINS , *PHEROMONES , *EUPLOTES - Abstract
The second of two diffusible cell signal proteins (pheromones) purified from a wild-type strain of the Antarctic ciliate, Euplotes nobilii, has been determined by automated Edman degradation of the whole molecule and peptides generated by its chymotryptic digestion. The proposed sequence of 52 amino acids of this new pheromone, designated En-1, is: NPEDWFTPDT10CAYGDSNTAW20TTCTTPGQTC30YTCCSSCFDV40VGEQACQMSA50QC. In common with the previously determined 60-amino-acid sequence of the other pheromone, En-2, it bears eight cysteines in conserved positions (presumably linked into four conserved intrachain disulfide bonds), and physicochemical features of potential significance for cold adaptation, such as a reduced hydrophobicity, an increased solvent accessibility, and an improved local backbone flexibility. However, En-1 diverges from En-2 for having evolved a threonine cluster in the place of a glycine cluster to apparently make more flexible a region that is likely functionally important. [Copyright &y& Elsevier]
- Published
- 2003
- Full Text
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25. Structural characterization of a protein pheromone from a cold-adapted (Antarctic) single-cell eukaryote, the ciliate Euplotes nobilii
- Author
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Alimenti, Claudio, Ortenzi, Claudio, Carratore, Vito, and Luporini, Pierangelo
- Subjects
- *
PROTOZOA , *CELL proliferation , *LIQUID chromatography - Abstract
Free-living species of ciliated Protozoa control their vegetative (mitotic) proliferation and mating (sexual) processes by diffusible, cell type-specific protein signals (pheromones). One of these molecules, designated En-2, was isolated from a species, Euplotes nobilii, living in the stably cold marine waters of Antarctica, and its complete amino acid sequence of 60 residues was determined by automated Edman degradation of the whole protein and peptides generated by trypsin digestion. The proposed sequence is: DIEDFYTSETCPYKNDSQLA20WDTCSGGTGNCGTVCCGQCF40SFPVSQSCAGMADSNDCPNA60. The En-2 structure appears to be characterized by an adaptive insertion of a glycine-rich motif potentially capable to confer more flexibility to a functionally critical region of the molecule. [Copyright &y& Elsevier]
- Published
- 2002
- Full Text
- View/download PDF
26. Structural characterization of mating pheromone precursors of the ciliate protozoan <em>Euplotes raikovi</em>.
- Author
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Miceli, Cristina, la Terza, Antoneila, Bradshaw, Ralph A., and Luporini, Pierangelo
- Subjects
- *
PHEROMONES , *CILIATA , *EUPLOTES , *POLYMERASE chain reaction , *OLIGONUCLEOTIDES , *GENES , *BIOCHEMISTRY - Abstract
The precursors of Euplotes raikovi pheromones Er-2 and Er-10 have been structurally characterized from the sequences of their coding regions that were amplified and cloned using the polymerase chain reaction and oligonucleotide primers corresponding to conserved sequences of the gene for pheromone Er-1. The predicted amino acid sequences contain 75 residues distributed through three domains: signal peptide, pro segment and mature pheromone. Despite the conservation of the overall length, there is variation in the size of the pro segments and of the mature pheromones. The comparison of the sequences shows a gradient of identity from the amino to the carboxyl terminus; the signal sequences are identical (with ≥ 95% identity in the nucleotide sequences), the pro segments more variable and the mature pheromones quite diverse. The processing site of the pro pheromones, to produce the mature forms, is apparently characterized by the unusual Xaa-Asp sequence. [ABSTRACT FROM AUTHOR]
- Published
- 1991
- Full Text
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27. Molecular Structures and Coding Genes of the Water-Borne Protein Pheromones of Euplotes petzi, an Early Diverging Polar Species of Euplotes.
- Author
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Pedrini, Bill, Suter‐Stahel, Thea, Vallesi, Adriana, Alimenti, Claudio, and Luporini, Pierangelo
- Subjects
- *
EUPLOTES , *PROTEIN structure , *PHEROMONES , *CELLULAR recognition , *NUCLEAR magnetic resonance , *MOLECULAR structure - Abstract
Euplotes is diversified into dozens of widely distributed species that produce structurally homologous families of water-borne protein pheromones governing self-/nonself-recognition phenomena. Structures of pheromones and pheromone coding genes have so far been studied from species lying in different positions of the Euplotes phylogenetic tree. We have now cloned the coding genes and determined the NMR molecular structure of four pheromones isolated from Euplotes petzi, a polar species which is phylogenetically distant from previously studied species and forms the deepest branching clade in the tree. The E. petzi pheromone genes have significantly shorter sequences than in other congeners, lack introns, and encode products of only 32 amino acids. Likewise, the three-dimensional structure of the E. petzi pheromones is markedly simpler than the three-helix up-down-up architecture previously determined in another polar species, Euplotes nobilii, and in a temperate-water species, Euplotes raikovi. Although sharing the same up-down-up architecture, it includes only two short α-helices that find their topological counterparts with the second and third helices of the E. raikovi and E. nobilii pheromones. The overall picture that emerges is that the evolution of Euplotes pheromones involves progressive increases in the gene sequence length and in the complexity of the three-dimensional molecular structure. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
28. Molecular cold-adaptation: Comparative analysis of two homologous families of psychrophilic and mesophilic signal proteins of the protozoan ciliate, Euplotes.
- Author
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Alimenti, Claudio, Vallesi, Adriana, Pedrini, Bill, Wüthrich, Kurt, and Luporini, Pierangelo
- Subjects
- *
PHEROMONES , *COMPARATIVE studies , *PROTEINS , *CILIATA , *EUPLOTES - Abstract
Locations of negatively charged and aromatic residues in En and Er pheromones. See Molecular Cold-adaptation: Comparative Analysis of Two Homologous Families of Psychrophilic and Mesophilic Signal Proteins of the Protozoan Ciliate, Euplotes by Alimenti et al., pp. 838–845 [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
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