Author/Editor		Malovrh, Petra; Viero, Gabriella; Dalla-Serra, Mauro; Podlesek, Zdravko; Lakey, Jeremy H; Maček, Peter; Menestrina, Gianfranco; Anderluh, Gregorq
Title		A novel mechanism of pore formation: membrane preparation by the N-terminal amphipathic region of equinatoxin
Type		članek
Source		J Biol Chem
Vol. and No.		Letnik 278, št. 25
Publication year		2003
Volume		str. 22678-85
Language		eng
Abstract		Equinatoxin II is a representatlve ot actinoporins, eukaryotic pore-forming toxins from sea anemones. It creates pares in natural and artifficial lipid membranes by an association of three or four monomers. Cysteinescanaing mutagenesis was used to study the structure of the N terminus, which is proposed to be crucial in transmembrane pore formation. We provide data for two steps of pore formation: a lipid-bound monomeric intermediate state and a flnal oligomeric pore. Results show that residues 10-28 are organized as an alpha-helix in both steps. In the first step, the whole region is transferred to a lipid-water interface, laying flat on the membrane. In the pore-forming state, the hydrophilic side of the amphipathic helix lines the pore lumen. The pore has a restriction around Asp-10, according to the permeabilization ratio of ions flowing through pores formed by chemically modified mutants. A general model was introduced to derive the tilt angle of the helix from the ion current data. This study reveals that actinoporins use a unique single helix insertion mechanism for pore formation.
Descriptors		CNIDARIAN VENOMS PORINS CELL MEMBRANE PERMEABILITY LIPID BILAYERS SEA ANEMONES ESCHERICHIA COLI MUTAGENESIS, SITE-DIRECTED CYSTEINE RECOMBINANT FUSION PROTEINS SPECTROMETRY, FLUORESCENCE