Person: Martínez Del Pozo, Álvaro
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First Name
Álvaro
Last Name
Martínez Del Pozo
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Bioquímica y Biología Molecular
Area
Bioquímica y Biología Molecular
Identifiers
2 results
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Item The metamorphic transformation of a water-soluble monomeric protein into an oligomeric transmembrane pore(Advances in Biomembranes and Lipid Self-Assembly, 2017) García Linares, Sara; Rivera de la Torre, Esperanza; Palacios Ortega, Juan; Gavilanes, José G.; Martínez Del Pozo, ÁlvaroSea anemones produce venoms containing different toxic molecules. Among them, actinoporins are some of the best characterized ones. They constitute a family of toxic polypeptides that belong to the much larger group of pore-forming toxins. Actinoporins remain mostly monomeric and stably folded in aqueous solution but, upon interaction with lipid membranes of specific composition, they become oligomeric integral membrane structures to build a pore. They insert an α-helix stretch within biological membranes, forming cation-selective pores with a diameter of 1–2 nm, which result in a colloid osmotic shock that leads to cell death. They are believed to participate in functions like predation, defense, and digestion and have been shown to be lethal for small crustaceans, mollusks, and fish. The best-known actinoporins are equinatoxin II (from Actinia equina), fragaceatoxin C (from Actinia fragacea), and sticholysins I and II (from Stichodactyla helianthus). In order to fully understand the pore formation mechanism of these proteins, several approaches have been used: (i) characterization of natural and artificial variants of actinoporins to determine the role of specific residues, (ii) study of their water-soluble and transmembrane structures, and (iii) employment of different lipids to evaluate the influence of membrane properties and composition. Further research is still needed, however, in order to fully understand the complex mechanism underlying actinoporins’ functionality.Item Evaluation of different approaches used to study membrane permeabilization by actinoporins on model lipid vesicles(Biochimica et Biophysica Acta (BBA) - Biomembranes, 2020) Palacios Ortega, Juan; Rivera-de-Torre, Esperanza; Gavilanes, José G.; Slotte, J. Peter; Martínez Del Pozo, ÁlvaroRelease of aqueous contents from model lipid vesicles has been a standard procedure to evaluate pore formation efficiency by actinoporins, such as sticholysin II (StnII), for the last few decades. However, regardless of the probe of choice, the results reported that StnII action was never able to empty the vesicles completely. This was hard to explain if StnII pores were to be stable and always leaky for the probes used. To address this question, we have used a variety of probes, including rhodamine 6G or Tb3+, to test the permeability of StnII's pores. Our results indicate that calcein was in fact too large to fit through StnII's pores, and that the standard method in the field is actually reporting StnII-induced transient permeation of the membrane rather than the passage of solutes through the stable assembled pores. In order to evaluate the permeability of these structures, we used a dithionite-based assay, which showed that the final pores were in fact open. Thus, our results indicate that the stable actinoporins' pores are open in spite of plateaued classic release curves. Besides the proper pore, the first stages of pore formation would inflict serious damage to living cells as well.