3lim
From Proteopedia
Crystal structure of the pore forming toxin frac from sea anemone actinia fragacea
Structural highlights
Function[ACTPC_ACTFR] 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.[1] Publication Abstract from PubMedPore-forming toxins (PFTs) are proteins that are secreted as soluble molecules and are inserted into membranes to form oligomeric transmembrane pores. In this paper, we report the crystal structure of Fragaceatoxin C (FraC), a PFT isolated from the sea anemone Actinia fragacea, at 1.8 A resolution. It consists of a crown-shaped nonamer with an external diameter of about 11.0 nm and an internal diameter of approximately 5.0 nm. Cryoelectron microscopy studies of FraC in lipid bilayers reveal the pore structure that traverses the membrane. The shape and dimensions of the crystallographic oligomer are fully consistent with the membrane pore. The FraC structure provides insight into the interactions governing the assembly process and suggests the structural changes that allow for membrane insertion. We propose a nonameric pore model that spans the membrane by forming a lipid-free alpha-helical bundle pore. Structural insights into the oligomerization and architecture of eukaryotic membrane pore-forming toxins.,Mechaly AE, Bellomio A, Gil-Carton D, Morante K, Valle M, Gonzalez-Manas JM, Guerin DM Structure. 2011 Feb 9;19(2):181-91. PMID:21300287[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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