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D-xylose, the main building block of plant biomass, is a pentose sugar that can be used by bacteria as a carbon source for bio-based fuel and chemical production through fermentation. In bacteria, the first step for D-xylose metabolism is signal perception at the membrane. We previously identified a three-component system in Firmicutes bacteria comprising a membrane-associated sensor protein (XylFII), a transmembrane histidine kinase (LytS) for periplasmic D-xylose sensing, and a cytoplasmic response regulator (YesN) that activates the transcription of the target ABC transporter xylFGH genes to promote the uptake of D-xylose. The molecular mechanism underlying signal perception and integration of these processes remains elusive, however. Here we purified the N-terminal periplasmic domain of LytS (LytSN) in a complex with XylFII and determined the conformational structures of the complex in its D-xylose--free and D-xylose--bound forms. LytSN contains a four-helix bundle, and XylFII contains two Rossmann fold-like globular domains with a xylose-binding cleft between them. In the absence of D-xylose, LytSN and XylFII formed a heterodimer. Specific binding of D-xylose to the cleft of XylFII induced a large conformational change that closed the cleft and brought the globular domains closer together. This conformational change led to the formation of an active XylFII-LytSN heterotetramer. Mutations at the D-xylose binding site and the heterotetramer interface diminished heterotetramer formation and impaired the D-xylose--sensing function of XylFII-LytS. Based on these data, we propose a working model of XylFII-LytS that provides a molecular basis for D-xylose utilization and metabolic modification in bacteria. [ABSTRACT FROM AUTHOR]

Lampreys possess two T-like lymphocyte lineages that express either variable lymphocyte receptor (VLR) A or VLRC antigen receptors. VLRA+ and VLRC+ lymphocytes share many similarities with the two principal T-cell lineages of jawed vertebrates expressing the αβ and γδ T-cell receptors (TCRs). During the assembly of VLR genes, several types of genomic cassettes are inserted, in step-wise fashion, into incomplete germ-line genes to generate the mature forms of antigen receptor genes. Unexpectedly, the structurally variable components of VLRA and VLRC receptors often possess partially identical sequences; this phenomenon of module sharing between these two VLR isotypes occurs in both lampreys and hagfishes. By contrast, VLRA and VLRC molecules typically do not share their building blocks with the structurally analogous VLRB receptors that are expressed by B-like lymphocytes. Our studies reveal that VLRA and VLRC germ-line genes are situated in close proximity to each other in the lamprey genome and indicate the interspersed arrangement of isotype-spe-cific and shared genomic donor cassettes; these features may facilitate the shared cassette use. The genomic structure of the VLRA/ VLRC locus in lampreys is reminiscent of the interspersed nature of the TCRA/TCRD locus in jawed vertebrates that also allows the sharing of some variable gene segments during the recombinatorial assembly of TCR genes. [ABSTRACT FROM AUTHOR]

Jawless vertebrates (cyclostomes) have an alternative adaptive immune system in which lymphocytes somatically diversify their variable lymphocyte receptors (VLR) through recombinatorial use of leucine-rich repeat cassettes during VLR gene assembly. Three types of these anticipatory receptors in lampreys (VLRA, VLRB, and VLRC) are expressed by separate lymphocyte lineages. However, only two VLR genes (VLRA and VLRB) have been found in hagfish. Here we have identified a third hagfish VLR, which undergoes somatic assembly to generate sufficient diversity to encode a large repertoire of anticipatory receptors. Sequence analysis, structural comparison, and phylogenetic analysis indicate that the unique hagfish VLR is the counterpart of lamprey VLRA and the previously identified hagfish "VLRA" is the lamprey VLRC counterpart. The demonstration of three orthologous VLR genes in both lampreys and hagfish suggests that this anticipatory receptor system evolved in a common ancestor of the two cyclostome lineages around 480 Mya. [ABSTRACT FROM AUTHOR]

Background: Lectins are sugar-binding proteins that specifically recognize sugar complexes. Based on the specificity of protein-sugar interactions, different lectins could be used as carrier molecules to target drugs specifically to different cells which express different glycan arrays. In spite of lectin's interesting biological potential for drug targeting and delivery, a potential disadvantage of natural lectins may be large size molecules that results in immunogenicity and toxicity. Smaller peptides which can mimic the function of lectins are promising candidates for drug targeting. Principal Findings: Small peptide with lectin-like behavior was screened from amphibian skin secretions and its structure and function were studied by NMR, NMR-titration, SPR and mutant analysis. A lectin-like peptide named odorranalectin was identified from skin secretions of Odorrana grahami. It was composed of 17 aa with a sequence of YASPKCFRYPNGVLACT. Lfucose could specifically inhibit the haemagglutination induced by odorranalectin. 125I-odorranalectin was stable in mice plasma. In experimental mouse models, odorranalectin was proved to mainly conjugate to liver, spleen and lung after i.v. administration. Odorranalectin showed extremely low toxicity and immunogenicity in mice. The small size and single disulfide bridge of odorranalectin make it easy to manipulate for developing as a drug targeting system. The cyclic peptide of odorranalectin disclosed by solution NMR study adopts a β-turn conformation stabilized by one intramolecular disulfide bond between Cys6-Cys16 and three hydrogen bonds between Phe7-Ala15, Tyr9-Val13, Tyr9-Gly12. Residues K5, C6, F7, C16 and T17 consist of the binding site of L-fucose on odorranalectin determined by NMR titration and mutant analysis. The structure of odorranalectin in bound form is more stable than in free form. Conclusion: These findings identify the smallest lectin so far, and show the application potential of odorranalectin for drug delivery and targeting. It also disclosed a new strategy of amphibian anti-infection. [ABSTRACT FROM AUTHOR]

The disulfide-bridged hendecapeptide (CWTKSIPPKPC) loop, derived from an amphibian skin peptide, is found to have strong trypsin inhibitory capability. This loop, called the trypsin inhibitory loop (TIL), appears to be the smallest serine protease inhibitor known. A series of synthetic peptides derived from this loop also exhibits trypsin inhibitory activity; some peptides even exhibit both antimicrobial and trypsin inhibitory activities. Antimicrobial peptides are attractive candidates for producing novel antibiotics, but their sensitivity to trypsin-like proteases appreciably limits their application. Bifunctional peptides with both antimicrobial and trypsin inhibitory activities could be ideal candidates for clinical antibiotics, since these reported synthetic peptides have shown resistance against trypsin. The crystal structure of a complex of trypsin with one TIL derivative is solved. The concept of TIL is introduced in this paper. Novel trypsin inhibitors or antimicrobial peptides can be designed readily on the basis of the TIL. Furthermore, functional analysis and a precursor comparison suggest that serine protease inhibitors may have a common ancestor with antimicrobial peptides. [ABSTRACT FROM AUTHOR]

Two neuropeptides were isolated from synganglia (central nervous system) of the hard tick, Ixodes sinensis. Their primary sequences were established as Leu-Val-Val-Tyr-Pro-Trp-Thr-Lys and Trp- Glu-Lys-Leu-Gly-Ser-Met-Glu-Thr-Leu. By hot plate bioassay, neuropeptide a displayed strong antinociceptive effect in mice by a dose-dependent behavior, while neuropeptide b had some relaxant effects on the isolated rat strip. These neuropeptides might be involved in down-regulating the host's defensive reaction. [ABSTRACT FROM AUTHOR]

Three types of variable lymphocyte receptor (VLR) genes, VLRA, VLRB, and VLRC, encode antigen recognition receptors in the extant jawless vertebrates, lampreys and hagfish. The somatically diversified repertoires of these VLRs are generated by serial stepwise copying of leucine-rich repeat (LRR) sequences into an incomplete germline VLR gene. Lymphocytes that express VLRA or VLRC are T cell–like, while VLRB-expressing cells are B cell–like. Here, we analyze the composition of the VLRB locus in different jawless vertebrates to elucidate its configuration and evolutionary modification. The incomplete germline VLRB genes of two hagfish species contain short noncoding intervening sequences, whereas germline VLRB genes in six representative lamprey species have much longer intervening sequences that exhibit notable genomic variation. Genomic clusters of potential LRR cassette donors, fragments of which are copied to complete VLRB gene assembly, are identified in Japanese lamprey and sea lamprey. In the sea lamprey, 428 LRR cassettes are located in five clusters spread over a total of 1.7 Mbp of chromosomal DNA. Preferential usage of the different donor cassettes for VLRB assemblage is characterized in our analysis, which reveals evolutionary modifications of the lamprey VLRB genes, elucidates the organization of the complex VLRB locus, and provides a comprehensive catalog of donor VLRB cassettes in sea lamprey and Japanese lamprey. [ABSTRACT FROM AUTHOR]

BAFF (TNF superfamily [TNFSF] 13B/Blys) and APRIL (TNFSF13) are important regulatory factors for lymphocyte activation and survival in mammals. A BAFF/APRIL-like relative called BAFF- and APRIL-like molecule (BALM) has also been identified in cartilaginous and bony fishes, and we report in this study a BAFF-like gene in lampreys. Our phylogenetic analysis of these genes and a related TNFSF12 gene called TNF-like weak inducer of apoptosis (TWEAK) suggest that, whereas an ancestral homolog of BAFF and APRIL was already present in a common ancestor of jawed and jawless vertebrates, TWEAK evolved early on in the jawed vertebrate lineage. Like mammalian BAFF and APRIL, the lamprey BAFF-like gene is expressed in T-like, B-like, and innate immune cells. The predicted protein encoded by this BAFF-like gene in lampreys exhibits higher sequence similarity with mammalian BAFF than APRIL. Correspondingly, we find BAFF orthologs in all of the jawed vertebrate representatives that we examined, although APRIL and/or BALM orthologs are not identifiable in certain jawed vertebrates. For example, BALM is not identifiable in tetrapods, and APRIL is not identifiable in several bony fishes or in birds, the latter of which also lack a TWEAK-like gene. Our analysis further suggests that a hybrid molecule called TWE-PRIL, which is a product of an in-genomic fusion between APRIL and TWEAK genes evolved early in mammalian evolution. [ABSTRACT FROM AUTHOR]

BAFF (TNF superfamily [TNFSF1 13B/BIys) and APRIL (TNFSF13) are important regulatory factors for lymphocyte activation and survival in mammals. A BAFF/APRIL-like relative called BAFF- and APRIL-like molecule (BALM) has also been identified in cartilaginous and bony fishes, and we report in this study a BAFF-like gene in lampreys. Our phylogenetic analysis of these genes and a related TNFSF12 gene called TNF-like weak inducer of apoptosis (TWEAK) suggest that, whereas an ancestral homolog of BAFF and APRIL was already present in a common ancestor of jawed and jawless vertebrates, TWEAK evolved early on in the jawed vertebrate lineage. Like mammalian BAFF and APRIL, the lamprey /M/'F-like gene is expressed in T-like, B-like, and innate immune cells. The predicted protein encoded by this BAFF-Uke gene in lampreys exhibits higher sequence similarity with mammalian BAFF than APRIL. Correspondingly, we find BAFF orthologs in all of the jawed vertebrate representatives that we examined, although APRIL and/or BALM orthologs are not identifiable in certain jawed vertebrates. For example. BALM is not identifiable in tetrapods, and APRIL is not identifiable in several bony fishes or in birds, the latter of which also lack a TWEA F-like gene. Our analysis further suggests that a hybrid molecule called TWE-PRIL, which is a product of an in-genomic fusion between APRIL and TWEAK genes evolved early in mammalian evolution. [ABSTRACT FROM AUTHOR]

Cathelicidins are a family of antimicrobial peptides acting as multifunctional effector molecules in innate immunity. Cathelicidin-BF has been purified from the snake venoms of Bungarus fasciatus and it is the first identified cathelicidin antimicrobial peptide in reptiles. In this study, cathelicidin-BF was found exerting strong antibacterial activities against Propionibacterium acnes. Its minimal inhibitory concentration against two strains of P. acnes was 4.7 &mgr;g/ml. Cathelicidin-BF also effectively killed other microorganisms including Staphylococcus epidermidis, which was possible pathogen for acne vulgaris. Cathelicidin-BF significantly inhibited pro-inflammatory factors secretion in human monocytic cells and P. acnesinduced O2 production of human HaCaT keratinocyte cells. Observed by scanning electron microscopy, the surfaces of the treated pathogens underwent obvious morphological changes compared with the untreated controls, suggesting that this antimicrobial peptide exerts its action by disrupting membranes of microorganisms. The efficacy of cathelicidin-BF gel topical administering was evaluated in experimental mice skin colonization model. In vivo anti-inflammatory effects of cathelicidin-BF were confirmed by relieving P. acnes-induced mice ear swelling and granulomatous inflammation. The antiinflammatory effects combined with potent antimicrobial activities and O2 production inhibition activities of cathelicidin- BF indicate its potential as a novel therapeutic option for acne vulgaris. [ABSTRACT FROM AUTHOR]

Ticks are blood-feeding arthropods that may secrete immunosuppressant molecules, which inhibit host inflammatory and immune responses and provide survival advantages to pathogens at tick bleeding sites in hosts. In the current work, two families of immnnoregulatory peptides, hyalomin-A and -B, were first identified from salivary glands of hard tick Hyalomma asiaticum asiaticum. Three copies of hyalomin-A are encoded by an identical gene and released from the same protein precursor. Both hyalomin-A and -B can exert significant anti-inflammatory functions, either by directly inhibiting host secretion of inflammatory factors such as tumor necrosis factor-α, monocyte chemotectic protein-1, and interferon-γ, or by indirectly increasing the secretion of immunosuppressant cytokine of interleukin-10. Hyalomin-A and -B were both found to potently scavenge free radical in vitro in a rapid manner and inhibited adjuvant-induced inflammation in mouse models in vivo. The INK/SAPK subgroup of the MAPK signaling pathway was involved in such immunoregulatory functions of hyalomin-A and -B. These results showed that immunoregulatory peptides of tick salivary glands suppress host inflammatory response by modulating cytokine secretion and detoxifying reactive oxygen species. [ABSTRACT FROM AUTHOR]

Jawless vertebrates use variable lymphocyte receptors (VLR) comprised of leucine-rich-repeat (LRR) segments as counterparts of the immunoglobulin-based receptors that jawed vertebrates use for antigen recognition. Highly diverse VLR genes are somatically assembled by the insertion of variable LRR sequences into incomplete germline VLRA and VLRB genes. Here we show that in sea lampreys (Petromyzon marinus) VLRA and VLRB anticipatory receptors are expressed by separate lymphocyte populations by monoallelic VLRA or VLRB assembly, together with expression of cytosine deaminase 1 (CDA1) or 2 (CDA2), respectively. Distinctive gene expression profiles for VLRA+ and VLRB+ lymphocytes resemble those of mammalian T and B cells. Although both the VLRA and the VLRB cells proliferate in response to antigenic stimulation, only the VLRB lymphocytes bind native antigens and differentiate into VLR antibody-secreting cells. Conversely, VLRA lymphocytes respond preferentially to a classical T-cell mitogen and upregulate the expression of the pro-inflammatory cytokine genes interleukin-17 (IL-17) and macrophage migration inhibitory factor (MIF). The finding of T-like and B-like lymphocytes in lampreys offers new insight into the evolution of adaptive immunity. [ABSTRACT FROM AUTHOR]

A correction to the article "Dual nature of the adaptive immune system in lampreys" that was published in the 2009 issue is presented.