Role of the Tryptophan Residues in the Specific Interaction of the Sea Anemone Stichodactyla helianthus’s Actinoporin Sticholysin II with Biological Membranes

Publication year: 2016
Authors: García-Linares S. 1, 2, Maula T. 2, Rivera-de-Torre E. 1, Gavilanes J.G. 1, Slotte J.P. 2, Martínez-del-Pozo A. 1
Affiliations:
1 - Departamento de Bioquímica y Biología Molecular I, Universidad Complutense, Madrid, Spain
2 - Biochemistry, Faculty of Science and Engineering, Åbo Akademi University, Turku, Finland
Published in: Biochemistry, 2016, Vol. 55 (46), p. 6406–6420
doi: 10.1021/acs.biochem.6b00935

Actinoporins are pore-forming toxins from sea anemones. Upon interaction with sphingomyelin-containing bilayers, they become integral oligomeric membrane structures that form a pore. Sticholysin II from Stichodactyla helianthus contains five tryptophans located at strategic positions; its role has now been studied using different mutants. Results show that W43 and W115 play a determinant role in maintaining the high thermostability of the protein, while W146 provides specific interactions for protomer–protomer assembly. W110 and W114 sustain the hydrophobic effect, which is one of the major driving forces for membrane binding in the presence of Chol. However, in its absence, additional interactions with sphingomyelin are required. These conclusions were confirmed with two sphingomyelin analogues, one of which had impaired hydrogen bonding properties. The results obtained support actinoporins’ Trp residues playing a major role in membrane recognition and binding, but their residues have an only minor influence on the diffusion and oligomerization steps needed to assemble a functional pore.


MP-SPR keywords: liposomes, protein binding to vesicles, toxins pore formation