DELTA-actitoxin-Afr1a

UniProtKB accession:  B9W5G6

Grouped By:  Matching UniProtKB accession

UniProtKB description:  Pore-forming toxin (PFT) that consists of a crown-shaped octamer or nonamer that forms cation-selective hydrophilic pores of about 1.5 nm (inside) and 13 nm (outside) (PubMed:21300287, PubMed:25716479). It causes cardiac stimulation and cytolysis (EC(50)=1.6 nM on erythrocytes) (PubMed:19563820, PubMed:25759390, PubMed:31295915). Interestingly, the Phe-16 is crucial for hemolysis (PubMed:25759390). 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 monomers (PubMed:19563820, PubMed:25716479). It is probable that a dimeric form is an assembly intermediate before the complete oligomerization (PubMed:25716479). The formation of stable pores occurs only in vesicles composed of DOPC/SM (there is no oligomerization when the PFT is treated with vesicles of DOPC or SM alone) (PubMed:25716479). The transmembrane pore displays 8 lateral perforations, one at each subunit-subunit interface, partially occupied by the acyl-chain region of a bridging lipid (PubMed:25716479). Each pore contains 24 lipid molecules, firmly bound to each subunit, that is, 3 lipids (L1, L2, L3, L4 and/or L5) are associated to each subunit (PubMed:25716479). Lipid L1 bridges 2 subunits, whereas lipids L2 and L3 bind to sites at single subunit (PubMed:25716479).