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Differential effect of membrane composition on the pore-forming ability of four fifferent sea Anemone Actinoporins



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García-Linares, Sara and Rivera de la Torre, Esperanza and Morante, Koldo and Tsumoto, Kouhei and Caaveiro, José M. M. and Gavilanes, José G. and Slotte, J. Peter and Martínez del Pozo, Álvaro (2016) Differential effect of membrane composition on the pore-forming ability of four fifferent sea Anemone Actinoporins. Biochemistry, 55 (48). pp. 6630-6641. ISSN 0006-2960, ESSN: 1520-4995

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Official URL: http://pubs.acs.org/doi/abs/10.1021/acs.biochem.6b01007


Sea anemone actinoporins constitute a protein family of multigene pore-forming toxins (PFT). Equinatoxin II (EqtII), fragaceatoxin C (FraC), and sticholysins I and II (StnI and StnII, respectively), produced by three different sea anemone species, are the only actinoporins whose molecular structures have been studied in depth. These four proteins show high sequence identities and practically coincident three-dimensional structures. However, their pore-forming activity can be quite different depending on the model lipid system employed, a feature that has not been systematically studied before. Therefore, the aim of this work was to evaluate and compare the influence of several distinct membrane conditions on their particular poreforming behavior. Using a complex model membrane system, such as sheep erythrocytes, StnII showed hemolytic activity much higher than those of the other three actinoporins studied. In lipid model systems, pore-forming ability when assayed against 4:1 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/sphingomyelin (SM) vesicles, with the membrane binding being the ratelimiting step, decreased in the following order: StnI > StnII > EqtII > FraC. When using 1:1:1 DOPC/SM/cholesterol LUVs, the presence of Chol not only enhanced membrane binding affinities by ∼2 orders of magnitude but also revealed how StnII was much faster than the other three actinoporins in producing calcein release. This ability agrees with the proposal that explains this behavior in terms of their high sequence variability along their first 30 N-terminal residues. The influence of interfacial hydrogen bonding in SM- or dihydro-SM-containing bilayers was also shown to be a generalized feature of the four actinoporins studied. It is finally hypothesized that this observed variable ability could be explained as a consequence of their distinct specificities and/or membrane binding affinities. Eventually, this behavior can be modulated by the nature of their natural target membranes or the interaction with not yet characterized isotoxin forms from the same sea anemone species.

Item Type:Article
Uncontrolled Keywords:Sea Anemone Actinoporins; Membrane composition
Subjects:Medical sciences > Biology > Biochemistry
ID Code:42775
Deposited On:18 May 2017 11:23
Last Modified:18 May 2017 11:49

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