1tzq
Crystal structure of the equinatoxin II 8-69 double cysteine mutant
OverviewOverview
Actinoporins are eukaryotic pore-forming proteins that create 2-nm pores in natural and model lipid membranes by the self-association of four monomers. The regions that undergo conformational change and form part of the transmembrane pore are currently being defined. It was shown recently that the N-terminal region (residues 10-28) of equinatoxin, an actinoporin from Actinia equina, participates in building of the final pore wall. Assuming that the pore is formed solely by a polypeptide chain, other parts of the toxin should constitute the conductive channel and here we searched for these regions by disulfide scanning mutagenesis. Only double cysteine mutants where the N-terminal segment 1-30 was attached to the beta-sandwich exhibited reduced hemolytic activity upon disulfide formation, showing that other parts of equinatoxin, particularly the beta-sandwich and importantly the C-terminal alpha-helix, do not undergo large conformational rearrangements during the pore formation. The role of the beta-sandwich stability was independently assessed via destabilization of a part of its hydrophobic core by mutations of the buried Trp117. These mutants were considerably less stable than the wild-type but exhibited similar or slightly lower permeabilizing activity. Collectively these results show that a flexible N-terminal region and stable beta-sandwich are pre-requisite for proper pore formation by the actinoporin family.
About this StructureAbout this Structure
1TZQ is a Single protein structure of sequence from Actinia equina. Full crystallographic information is available from OCA.
ReferenceReference
Pore formation by equinatoxin, a eukaryotic pore-forming toxin, requires a flexible N-terminal region and a stable beta-sandwich., Kristan K, Podlesek Z, Hojnik V, Gutierrez-Aguirre I, Guncar G, Turk D, Gonzalez-Manas JM, Lakey JH, Macek P, Anderluh G, J Biol Chem. 2004 Nov 5;279(45):46509-17. Epub 2004 Aug 20. PMID:15322132 Page seeded by OCA on Sat May 3 10:34:00 2008