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Two major proteins, a-sarcin and an antifungal polypeptide AFP , are secreted by the mould Ž . Aspergillus giganteus MDH 18894 when it is cultured for 70–80 h. A third major protein is also found in the extracellular medium at 48–60 h, but it disappears as the culture proceeds. This protein has been isolated and characterized in terms of apparent molecular mass, electrophoretic and chromatographic behaviour, NH -terminal primary structure, amino acid content, spectroscopical 2 features, reactivity against anti-AFP antibodies, and antifungal activity. Based on the obtained results it would be an extracellular inactive precursor form of AFP, designated as the large form of AFP lf-AFP . Its amino acid composition is Ž . identical to that of AFP but containing six extra residues. NH -terminal sequence analysis of the first eight amino acid 2 residues of this polypeptide revealed that the extra residues can be perfectly accommodated within the DNA-deduced sequence of the precursor form of AFP. Its alignment with precursor sequences of different proteins, secreted by a variety of Aspergillus spp., reveals the existence of a common tetrapeptide at the carboxy-terminal end of their leader peptides. This sequence would be IlerLeu-Xaa-Yaa-Arg, being mostly Xaa and Yaa an acid residue Asp Ž . rGlu and alanine, respectively. The presence of lf-AFP as an extracellular protein would be in perfect agreement with the existence of this tetrapeptide motif, that can be involved in the protein secretion mechanisms of filamentous fungi., Depto. de Bioquímica y Biología Molecular, Fac. de Ciencias Químicas, TRUE, pub

a-Sarcin, restrictocin and mitogillin are the best known members of the family of fungal ribotoxins. In recent years, new members of this family have been discovered and characterised. In this work, we study the occurrence of ribotoxins among di erent species of fungi. The presence of ribotoxins has been identi®ed in some new species by means of genetic studies, as well as expression and activity assays. The ribotoxin genes have been partially sequenced, and demonstrate a high degree of similarity. These studies demonstrate that these toxins are more widespread than previously considered. This is surprising, considering the ribotoxins are such speci®c and potent toxins, of unknown biological function. These studies con®rm the hypothesis that these proteins are naturally engineered toxins derived from ribonucleases of broad substrate speci®city., Depto. de Bioquímica y Biología Molecular, Fac. de Ciencias Químicas, TRUE, pub

Sticholysins are pore-forming toxins produced by the sea anemone Stichodactyla helianthus. When they encounter a sphingomyelin-containing membrane, these proteins bind to it and oligomerize, a process that ends in pore formation. Mounting evidence indicates that StnII can favour the activity of StnI. Previous results have shown that these two isotoxins can oligomerize together. Furthermore, StnII appeared to potentiate the activity of StnI through the membrane-binding step of the process. Hence, isotoxin interaction should occur prior to membrane encounter. Here, we have used analytical ultracentrifugation to investigate the oligomerization of Stns in solution, both separately and together. Our results indicate that while StnI seems to be more prone to oligomerize in water solution than StnII, a small percentage of StnII in StnI-StnII mixtures promotes oligomerization.

Azúcares, hidratos de carbono, fibra, grasas o lípidos, minerales, proteínas y vitaminas son los componentes básicos de los alimentos, son las moléculas que comemos. ¿Cuáles son sus propiedades? ¿Por qué son importantes para nuestro desarrollo y salud? ¿Cómo proporcionan a los alimentos sus diferentes aromas, colores, sabores y texturas? ¿Qué tipo de reacciones químicas se producen al cocinar? ¿Qué enfermedades están vinculadas a la dieta? ¿Por qué los llamados superalimentos son falsos mitos de la alimentación? Esta obra es una guía didáctica que responde a estas y a otras preguntas que cualquiera se habrá planteado en algún momento sobre la alimentación y sobre las moléculas presentes en nuestra dieta. Con sencillas explicaciones y una amplia variedad de experimentos y talleres, en versión bilingüe español-inglés, que pueden hacerse tanto en la cocina de casa como en el colegio, este libro da a conocer la bioquímica de nuestra alimentación. Las moléculas que comemos está adaptado a los niveles educativos de primaria y secundaria.

The identification or design of biocatalysts to mitigate the accumulation of plastics, including sub-micro- and nano-sized polyethylene terephthalate (nPET), is becoming a global challenge. Here we computationally incorporated two hydrolytic active sites with geometries similar to that of Idionella sakaiensis PET hydrolase, to fragaceatoxin C (FraC), a membrane pore-forming protein. FraCm1/m2 could be assembled into octameric nanopores (7.0 nm high × 1.6–6.0 nm entry), which deconstructed (40 °C, pH 7.0) nPET from GoodFellow, commodities and plastic bottles. FraCm1 and FraCm2 degrade nPET by endo- and exo-type chain scission. While FraCm1 produces bis(2-hydroxyethyl) terephthalate as the main product, FraCm2 yields a high diversity of oligomers and terephthalic acid. Mechanistic and biochemical differences with benchmark PET hydrolases, along with pore and nPET dynamics, suggest that these pore-forming protein catalytic nanoreactors do not deconstruct macro-PET but are promising in nanotechnology for filtering, capturing and breaking down nPET, for example, in wastewater treatment plants. [Figure not available: see fulltext.]. © 2023, The Author(s).

The usefulness of toxicity across the tree of life is far beyond doubt. Most, if not all, organisms produce compounds that can be used for attack and/or defense against external entities. Some of the most specialized of these compounds are toxic proteins, among which pore-forming toxins (PFTs) particularly excel. PFTs are present in all kingdoms of life. Given the wide variety of PFTs, one can expect a multitude of different specificities and mechanisms of action, of which we will certainly take advantage at some point. For that, a thorough characterization of PFTs and their functionality is necessary. In this thesis, we have taken further the characterization of sticholysins, small PFTs produced by the sea anemone Stichodactyla helianthus...

The usefulness of toxicity across the tree of life is far beyond doubt. Most, if not all, organisms produce compounds that can be used for attack and/or defense against external entities. Some of the most specialized of these compounds are toxic proteins, among which pore-forming toxins (PFTs) particularly excel. PFTs are present in all kingdoms of life. Given the wide variety of PFTs, one can expect a multitude of different specificities and mechanisms of action, of which we will certainly take advantage at some point. For that, a thorough characterization of PFTs and their functionality is necessary. In this thesis, we have taken further the characterization of sticholysins, small PFTs produced by the sea anemone Stichodactyla helianthus..., La toxicidad es indudablemente útil para los seres vivos. La mayoría, si no todos los organismos, producen compuestos para usarlos contra otros seres vivos, ya sea confines de defensa o de ataque. Algunos de los más especializados de estos compuestos son las proteínas tóxicas, entre las que destacan las toxinas formadoras de poros (ing.,pore-forming toxins, PFT). Estas proteínas pueden encontrarse en todos los reinos dela vida. Dada su amplia diversidad, puede esperarse que tengan una gran variedad de especificidades y mecanismos de acción. Una caracterización detallada de las PFT y su funcionalidad es un requisito fundamental para, en un futuro, poder beneficiarse dela acción de estas toxinas. Por ello, en esta tesis se ha profundizado en el comportamiento de las esticolisinas, pequeñas PFT producidas por la anémona del mar Caribe Stichodactyla helianthus..., Nyttan av toxicitet hos olika organismer är långt bortom tvivel. De flesta, om inte alla,organismer producerar föreningar som kan användas för attack och/eller försvar motexterna hot. Några av de mest specialiserade av dessa föreningar är toxiska proteiner,bland vilka por-bildande toxiner (eng., pore-forming toxins, PFT) är särskiltutmärkande. PFT finns i alla livets riken. Med tanke på det stora utbudet av PFT kanman förvänta sig en mängd olika specificiteter och verkningsmekanismer, som vi kankomma att dra nytta i olika tillämpningar. Därför är en grundlig karakterisering avPFT-peptider och deras funktionalitet nödvändig. I denna avhandling har viundersökt och karakteriser olika stickolysiner, vilka är små PFT-peptider produceradeav havsanemonen Stichodactyla helianthus...

The ribotoxin α-sarcin belongs to a family of ribonucleases that cleave the sarcin/ricin loop (SRL), a critical functional rRNA element within the large ribosomal subunit (60S), thereby abolishing translation. Whether α-sarcin targets the SRL only in mature 60S subunits remains unresolved. Here, we show that, in yeast, α-sarcin can cleave SRLs within late 60S pre-ribosomes containing mature 25S rRNA but not nucleolar/nuclear 60S pre-ribosomes containing 27S pre-rRNA in vivo. Conditional expression of α-sarcin is lethal, but does not impede early pre-rRNA processing, nuclear export and the cytoplasmic maturation of 60S pre-ribosomes. Thus, SRL-cleaved containing late 60S pre-ribosomes seem to escape cytoplasmic proofreading steps. Polysome analyses revealed that SRL-cleaved 60S ribosomal subunits form 80S initiation complexes, but fail to progress to the step of translation elongation. We suggest that the functional integrity of a α-sarcin cleaved SRL might be assessed only during translation.

Las proteínas formadoras de poros (PFP) son una familia de toxinas capaces de matar células por choque osmótico, precisamente porque forman poros en sus membranas. En disolución acuosa, estas proteínas permanecen plegadas y estables. Al interactuar con un receptor específico de la membrana (proteína, lípido o azúcar), se unen a ella, oligomerizan y forman un poro a través del núcleo hidrófobo de la membrana. Las actinoporinas son α-PFPs producidas por anémonas marinas como parte de su cóctel venenoso. Son pequeñas (≈ 20 kDa) y suelen tener un punto isoeléctrico básico ( ≈ 9). Comparten un motivo conformacional común, caracterizado por un sándwich β flanqueado por dos hélices α. Su receptor de membrana específico es la esfingomielina. Cuando las actinoporinas se unen a una membrana que contiene este esfingolípido, extienden su segmento helicoidal N-terminal, oligomerizan y forman un poro selectivo de cationes, insertando sus hélices α del extremo N-terminal a través del núcleo de la membrana. Sin embargo, el orden específico de las etapas que conducen a la formación del poro, así como la naturaleza de posibles estados intermedios, o su estequiometría final, todavía son objeto de debate. Estas actinoporinas constituyen además familias multigénicas: una sola especie produce una variedad de toxinas similares que no necesariamente muestran una actividad lítica o una especificidad idénticas. Debido a su simplicidad, son un modelo apropiado para estudiar la todavía no bien comprendida transición de una proteína soluble en agua a un estado en el que se integra en membrana...

I.amAble ha ofrecido a estudiantes universitarios de física, química, veterinaria, biología y educación la oportunidad de complementar su formación mediante el diseño, la realización y la evaluación de talleres científicos que faciliten la inclusión de personas con diversidad cognitiva. Los talleres han sido diseñados por el alumnado universitario de ciencias y perfilados por estudiantes de educación para ser llevados a cabo por alumnado preuniversitario en parejas, de forma que un miembro pertenezca a un centro de secundaria ordinario y el otro miembro a un centro de educación especial. Aquellos talleres que se han considerado más adecuados por su adaptabilidad se han llevado a la práctica guiados por estudiantes de ciencias y de educación. Los miembros del proyecto, que incluyen representantes de todos los estamentos universitarios, han supervisado todas las tareas descritas anteriormente. Además de los miembros de la Universidad Complutense, también figuran personas voluntarias de otras instituciones científicas y educativas. El alumnado universitario ha tenido la posibilidad, no sólo de asentar y profundizar algunos contenidos científicos o poner en práctica algunas de las enseñanzas adquiridas, sino también de desarrollar su empatía, su capacidad de comunicar e improvisar y de adaptarse a un público heterogéneo. Ello ha mejorado sus perspectivas laborales, especialmente dentro de la educación formal e informal (animación sociocultural, museos científicos...). Además, han contribuido a facilitar la inclusión educativa de las personas con diversidad funcional y a mejorar la cultura científica de la sociedad. Con este proyecto, inspirado en la metodología Aprendizaje-Servicio (ApS), se ha pretendido también mejorar la accesibilidad a las experiencias y contenidos científicos y facilitar la inclusión educativa de las personas con diversidad funcional, especialmente diversidad cognitiva o intelectual. En la primera edición de I.amAble (2016-17) se hizo hincapié en e

Venoms constitute complex mixtures of many different molecules arising from evolution in processes driven by continuous prey–predator interactions. One of the most common compounds in these venomous cocktails are pore-forming proteins, a family of toxins whose activity relies on the disruption of the plasmatic membranes by forming pores. The venom of sea anemones, belonging to the oldest lineage of venomous animals, contains a large amount of a characteristic group of pore-forming proteins known as actinoporins. They bind specifically to sphingomyelin-containing membranes and suffer a conformational metamorphosis that drives them to make pores. This event usually leads cells to death by osmotic shock. Sticholysins are the actinoporins produced by Stichodactyla helianthus. Three different isotoxins are known: Sticholysins I, II, and III. They share very similar amino acid sequence and three-dimensional structure but display different behavior in terms of lytic activity and ability to interact with cholesterol, an important lipid component of vertebrate membranes. In addition, sticholysins can act in synergy when exerting their toxin action. The subtle, but important, molecular nuances that explain their different behavior are described and discussed throughout the text. Improving our knowledge about sticholysins behavior is important for eventually developing them into biotechnological tools.

All metazoans depend on the consumption of O2 by the mitochondrial oxidative phosphorylation system (OXPHOS) to produce energy. In addition, the OXPHOS uses O2 to produce reactive oxygen species that can drive cell adaptations1,2,3,4, a phenomenon that occurs in hypoxia4,5,6,7,8 and whose precise mechanism remains unknown. Ca2+ is the best known ion that acts as a second messenger9, yet the role ascribed to Na+ is to serve as a mere mediator of membrane potential10. Here we show that Na+ acts as a second messenger that regulates OXPHOS function and the production of reactive oxygen species by modulating the fluidity of the inner mitochondrial membrane. A conformational shift in mitochondrial complex I during acute hypoxia11 drives acidification of the matrix and the release of free Ca2+ from calcium phosphate (CaP) precipitates. The concomitant activation of the mitochondrial Na+/Ca2+ exchanger promotes the import of Na+ into the matrix. Na+ interacts with phospholipids, reducing inner mitochondrial membrane fluidity and the mobility of free ubiquinone between complex II and complex III, but not inside supercomplexes. As a consequence, superoxide is produced at complex III. The inhibition of Na+ import through the Na+/Ca2+ exchanger is sufficient to block this pathway, preventing adaptation to hypoxia. These results reveal that Na+ controls OXPHOS function and redox signalling through an unexpected interaction with phospholipids, with profound consequences for cellular metabolism.