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Biochim Biophys Acta. 2016 Mar;1858(3):446-56. doi: 10.1016/j.bbamem.2015.09.007. Epub 2015 Sep 6.

Pore formation by actinoporins, cytolysins from sea anemones.

Author information

1
Laboratory for Molecular Biology and Nanobiotechnology, National Institute of Chemistry, Hajdrihova 19, 1000 Ljubljana, Slovenia.
2
Istituto di Biofisica, Consiglio Nazionale delle Ricerche & Fondazione Bruno Kessler, via alla Cascata 56/C, 38123 Trento, Italy.
3
Department of Biology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia.
4
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.

Abstract

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.

KEYWORDS:

Actinoporin; Equinatoxin; Fragaceatoxin; Pore formation; Sphingomyelin; Sticholysin

PMID:
26351738
DOI:
10.1016/j.bbamem.2015.09.007
[Indexed for MEDLINE]
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