Pore formation by actinoporins, cytolysins from sea anemones.
Actinoporins (APs) from sea anemones are ~20 kDa pore forming toxins with a β-sandwich structure flanked by two α-helices. The molecular mechanism of APs pore formation is composed of several well-defined steps. APs bind to membrane by interfacial binding site composed of several aromatic amino acid residues that allow binding to phosphatidylcholine and specific recognition of sphingomyelin. Subsequently, the N-terminal α-helix from the β-sandwich has to be inserted into the lipid/water interphase in order to form a functional pore. Functional studies and single molecule imaging revealed that only several monomers, 3-4, oligomerise to form a functional pore. In this model the α-helices and surrounding lipid molecules build toroidal pore. In agreement, AP pores are transient and electrically heterogeneous. On the contrary, crystallized oligomers of actinoporin fragaceatoxin C were found to be composed of eight monomers with no lipids present between the adjacent α-helices. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Maur Dalla Serra and Franco Gambale.
Laboratory for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia.
Nejc
N
Rojko
Istituto di Biofisica, Consiglio Nazionale delle Ricerche & Fondazione Bruno Kessler, via alla Cascata 56/C, 38123 Trento, Italy.
Mauro
M
Dalla Serra
Department of Biology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia.
Peter
P
Maček
Laboratory for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia; Department of Biology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia. Electronic address: gregor.anderluh@ki.si.
Gregor
G
Anderluh
D000818:Animals; D003064:Cnidarian Venoms / Q000737:chemistry* / Q000378:metabolism; D054353:Perforin / Q000737:chemistry* / Q000378:metabolism; D018272:Porins / Q000737:chemistry* / Q000378:metabolism; D017433:Protein Structure, Secondary; D012615:Sea Anemones / Q000737:chemistry* / Q000378:metabolism
D003064:Cnidarian Venoms; D018272:Porins; D054353:Perforin
Actinoporin; Equinatoxin; Fragaceatoxin; Pore formation; Sphingomyelin; Sticholysin