Structural highlights
Function
[ACTP2_ACTEQ] Pore-forming protein that forms cations-selective hydrophilic pores of around 1 nm and causes cardiac stimulation and hemolysis. Pore formation is a multi-step process that involves specific recognition of membrane sphingomyelin (but neither cholesterol nor phosphatidylcholine) using aromatic rich region and adjacent phosphocholine (POC) binding site, firm binding to the membrane (mainly driven by hydrophobic interactions) accompanied by the transfer of the N-terminal region to the lipid-water interface and finally pore formation after oligomerization of several monomers. Cytolytic effects include red blood cells hemolysis, platelet aggregation and lysis, cytotoxic and cytostatic effects on fibroblasts. Lethality in mammals has been ascribed to severe vasospasm of coronary vessels, cardiac arrhythmia, and inotropic effects.
Evolutionary Conservation
Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf.
Publication Abstract from PubMed
BACKGROUND: Membrane pore-forming toxins have a remarkable property: they adopt a stable soluble form structure, which, when in contact with a membrane, undergoes a series of transformations, leading to an active, membrane-bound form. In contrast to bacterial toxins, no structure of a pore-forming toxin from an eukaryotic organism has been determined so far, an indication that structural studies of equinatoxin II (EqtII) may unravel a novel mechanism. RESULTS: The crystal structure of the soluble form of EqtII from the sea anemone Actinia equina has been determined at 1.9 A resolution. EqtII is shown to be a single-domain protein based on a 12 strand beta sandwich fold with a hydrophobic core and a pair of alpha helices, each of which is associated with the face of a beta sheet. CONCLUSIONS: The structure of the 30 N-terminal residues is the largest segment that can adopt a different structure without disrupting the fold of the beta sandwich core. This segment includes a three-turn alpha helix that lies on the surface of a beta sheet and ends in a stretch of three positively charged residues, Lys-30, Arg-31, and Lys-32. On the basis of gathered data, it is suggested that this segment forms the membrane pore, whereas the beta sandwich structure remains unaltered and attaches to a membrane as do other structurally related extrinsic membrane proteins or their domains. The use of a structural data site-directed mutagenesis study should reveal the residues involved in membrane pore formation.
Crystal structure of the soluble form of equinatoxin II, a pore-forming toxin from the sea anemone Actinia equina.,Athanasiadis A, Anderluh G, Macek P, Turk D Structure. 2001 Apr 4;9(4):341-6. PMID:11525171[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Athanasiadis A, Anderluh G, Macek P, Turk D. Crystal structure of the soluble form of equinatoxin II, a pore-forming toxin from the sea anemone Actinia equina. Structure. 2001 Apr 4;9(4):341-6. PMID:11525171
