Rivera de Torre, EsperanzaPalacios Ortega, JuanGarcía Linares, SaraGavilanes, José G.Martínez Del Pozo, Álvaro2023-06-172023-06-172017-1210.1016/j.abb.2017.11.005https://hdl.handle.net/20.500.14352/18263Sticholysins I and II (StnI and StnII), α-pore forming toxins from the sea anemone Stichodactyla helianthus, are water-soluble toxic proteins which upon interaction with lipid membranes of specific composition bind to the bilayer, extend and insert their N-terminal α-helix, and become oligomeric integral membrane structures. The result is a pore that leads to cell death by osmotic shock. StnI and StnII show 93% of sequence identity, but also different membrane pore-forming activities. The hydrophobicity profile along the first 18 residues revealed differences which were canceled by substituting StnI amino acids 2 and 9. Accordingly, the StnID9A mutant, and the corresponding StnIE2AD9A variant, showed enhanced hemolytic activity. They also revealed a key role for an exposed salt bridge between Asp9 and Lys68. This interaction is not possible in StnII but appears conserved in the other two well-characterized actinoporins, equinatoxin II and fragaceatoxin C. The StnII mutant A8D showed that this single replacement was enough to transform StnII into a version with impaired pore-forming activity. Overall, the results show the key importance of this salt bridge linking the N-terminal stretch to the β-sandwich core. A conclusion of general application for the understanding of salt bridges role in protein design, folding and stability.engjournal articlehttp://www.sciencedirect.com/science/article/pii/S000398611730632X?via%3Dihubrestricted access577.1Pore-forming-toxinEquinatoxinFragaceatoxinOligomerizationIon-channelBioquímica (Química)