|SMART accession number:||SM00630|
|Interpro abstract (IPR001627):|
The Sema domain occurs in semaphorins, which are a large family of secreted and transmembrane proteins, some of which function as repellent signals during axon guidance. Sema domains also occur in a hepatocyte growth factor receptor, in SEX protein [(PUBMED:9875845)] and in viral proteins.
CD100 (also called SEMA4D) is associated with PTPase and serine kinase activity. CD100 increases PMA, CD3 and CD2 induced T cell proliferation, increases CD45 induced T cell adhesion, induces B cell homotypic adhesion and down-regulates B cell expression of CD23.
The Sema domain is characterised by a conserved set of cysteine residues, which form four disulphide bonds to stabilise the structure. The Sema domain fold is a variation of the beta propeller topology, with seven blades radially arranged around a central axis. Each blade contains a four- stranded (strands A to D) antiparallel beta sheet. The inner strand of each blade (A) lines the channel at the centre of the propeller, with strands B and C of the same repeat radiating outward, and strand D of the next repeat forming the outer edge of the blade. The large size of the Sema domain is not due to a single inserted domain but results from the presence of additional secondary structure elements inserted in most of the blades. The Sema domain uses a 'loop and hook' system to close the circle between the first and the last blades. The blades are constructed sequentially with an N-terminal beta- strand closing the circle by providing the outermost strand (D) of the seventh (C-terminal) blade. The beta-propeller is further stabilised by an extension of the N terminus, providing an additional, fifth beta-strand on the outer edge of blade 6 [(PUBMED:12925274), (PUBMED:12958590), (PUBMED:15167892)].
|GO function:||protein binding (GO:0005515)|
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- Evolution (species in which this domain is found)
- Metabolism (metabolic pathways involving proteins which contain this domain)
- Structure (3D structures containing this domain)
- Links (links to other resources describing this domain)