Protein: DELTA-stichotoxin-She4b (DELTA-SHTX-She4b) (Cytolysin III) (Sticholysin II) (St II) (St-II) (StII) (StnII) (Sticholysin-2) (STCH2) (P07845)
Organism: Stichodactyla helianthus (Sun anemone) (Stoichactis helianthus)
Function: Pore-forming protein that forms cations-selective hydrophilic pores of around 1 nm and causes cardiac stimulation and cytolysis. 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. 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.
Subcellular location: Secreted. Nematocyst {ECO:0000269|PubMed:16432881}. Target cell membrane {ECO:0000269|PubMed:17573423}. Note=Forms an alpha-helical membrane channel in the prey. {ECO:0000269|PubMed:17573423}.
Sequence: ALAGTIIAGASLTFQVLDKVLEELGKVSRKIAVGIDNESGGTWTALNAYFRSGTTDVILPEFVPNTKALLYSGRKDTGPVATGAVAAFAYYMSSGNTLGVMFSVPFDYNWYSNWWDVKIYSGKRRADQGMYEDLYYGNPYRGDNGWHEKNLGYGLRMKGIMTSAGEAKMQIKISR
InterPro domains: - IPR015926: Cytolysin/lectin (homologous_superfamily) [1-175]
- IPR009104: Sea anemone actinoporin-like (family) [2-175]
- IPR050677: Actinoporin Pore-Forming Toxin (family) [4-168]
Gene Ontology annotations:
Molecular Function (MF): GO:0003674 (molecular function), GO:0005488 (binding), GO:0005515 (protein binding), GO:0042802 (identical protein binding)
Biological Process (BP): GO:0008150 (biological process), GO:0065007 (biological regulation), GO:0050896 (response to stimulus), GO:0050789 (regulation of biological process), GO:0044419 (biological process involved in interspecies interaction between organisms), GO:0048519 (negative regulation of biological process), GO:0009605 (response to external stimulus), GO:0043903 (regulation of biological process involved in symbiotic interaction), GO:0009607 (response to biotic stimulus), GO:0050794 (regulation of cellular process), GO:0048583 (regulation of response to stimulus), GO:0002682 (regulation of immune system process), GO:0006950 (response to stress), GO:0048525 (negative regulation of viral process), GO:0051707 (response to other organism), GO:0048585 (negative regulation of response to stimulus), GO:0002831 (regulation of response to biotic stimulus), GO:0050776 (regulation of immune response), GO:0043207 (response to external biotic stimulus), GO:0009611 (response to wounding), GO:0080134 (regulation of response to stress), GO:0009617 (response to bacterium), GO:0006952 (defense response), GO:0032101 (regulation of response to external stimulus), GO:0002832 (negative regulation of response to biotic stimulus), GO:0098542 (defense response to other organism), GO:0031348 (negative regulation of defense response), GO:0032102 (negative regulation of response to external stimulus), GO:0031347 (regulation of defense response), GO:0045088 (regulation of innate immune response), GO:0042742 (defense response to bacterium), GO:0009893 (positive regulation of metabolic process), GO:0050829 (defense response to Gram-negative bacterium), GO:0050830 (defense response to Gram-positive bacterium)
Cellular Component (CC): GO:0005575 (cellular component), GO:0110165 (cellular anatomical entity), GO:0005576 (extracellular region)