title: Differential Effect of Membrane Composition on the Pore-Forming Ability of Four Different Sea Anemone Actinoporins.
abstract: 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 pore-forming 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 rate-limiting 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.
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , Madrid, Spain.|Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , Turku, Finland.
authors.forename: Sara
authors.initials: S
authors.lastname: García-Linares
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , Madrid, Spain.
authors.forename: Esperanza
authors.initials: E
authors.lastname: Rivera-de-Torre
authors.affiliation: Department of Bioengineering, Graduate School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Koldo
authors.initials: K
authors.lastname: Morante
authors.affiliation: Department of Bioengineering, Graduate School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Kouhei
authors.initials: K
authors.lastname: Tsumoto
authors.affiliation: Department of Bioengineering, Graduate School of Engineering, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Jose M M
authors.initials: JM
authors.lastname: Caaveiro
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , Madrid, Spain.
authors.forename: José G
authors.initials: JG
authors.lastname: Gavilanes
authors.affiliation: Biochemistry, Faculty of Science and Engineering, Åbo Akademi University , Turku, Finland.
authors.forename: J Peter
authors.initials: JP
authors.lastname: Slotte
authors.affiliation: Departamento de Bioquímica y Biología Molecular I, Universidad Complutense , Madrid, Spain.
authors.forename: Álvaro
authors.initials: Á
authors.lastname: Martínez-Del-Pozo
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D002784:Cholesterol / Q000737:chemistry / Q000378:metabolism; D002942:Circular Dichroism / Q000379:methods; D003064:Cnidarian Venoms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006461:Hemolysis; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D009930:Organic Chemicals / Q000737:chemistry / Q000378:metabolism; D010713:Phosphatidylcholines / Q000737:chemistry / Q000378:metabolism; D052899:Pore Forming Cytotoxic Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D012615:Sea Anemones / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D012756:Sheep; D013109:Sphingomyelins / Q000737:chemistry / Q000378:metabolism; D020349:Surface Plasmon Resonance
chemical_list: D003064:Cnidarian Venoms; D008051:Lipid Bilayers; D009930:Organic Chemicals; D010713:Phosphatidylcholines; D052899:Pore Forming Cytotoxic Proteins; D013109:Sphingomyelins; C545670:fragaceatoxin C; C404794:sticholysin II; C121348:stycholysin I; C012307:equinatoxin; D002784:Cholesterol; C017251:1,2-oleoylphosphatidylcholine