tetraspanin tetraspanin tetraspanins are a family of membrane proteins found in all multicellular eukaryotes. tetraspanin familytetraspanins have four transmembrane domains, two extracellular loops and contain a series of highly conserved amino acid residues.identifierssymboltetraspaninpfampf00335pfam clancl0347interproipr000301prositepdoc00371scop21iv5 / scope / supfamtcdb8.a.40opm superfamily327opm protein5tcxcddcd03127available protein structures:pfam structures / ecod pdbrcsb pdb; pdbe; pdbjpdbsumstructure summary hypothetical model of the tetraspanin function tetraspanins, also referred to as the transmembrane 4 superfamily (tm4sf) proteins, have four transmembrane alpha-helices and two extracellular domains, one short (called the small extracellular domain or loop, sed/sel or ec1) and one longer, typically 100 amino acid residues (the large extracellular domain/loop, led/lel or ec2). although several protein families have four transmembrane alpha-helices, tetraspanins are defined by conserved amino acid sequences including four or more cysteine residues in the ec2 domain, with two in a highly conserved 'ccg' motif. tetraspanins are often thought to act as scaffolding proteins, anchoring multiple proteins to one area of the cell membrane. tetraspanins are highly conserved between species. some tetraspanins can have n-linked glycosylations on the long extracellular loop (lel, ec2) and palmitoylations at a cxxc motif in their transmembrane region. there are 34 tetraspanins in mammals, 33 of which have also been identified in humans. tetraspanins display numerous properties that indicate their physiological importance in cell adhesion, motility, activation, and proliferation, as well as their contribution to pathological conditions such as metastasis or viral infection. a role for tetraspanins in platelets was demonstrated by the bleeding phenotypes of cd151- and tssc6-deficient mice, which exhibit impaired "outside-in" signalling through αiibβ3, the major platelet integrin. it is hypothesized that tetraspanins interact with and regulate other platelet receptors. list of human tetraspanins protein gene aliases tspan1 tspan1 tsp-1 tspan2 tspan2 tsp-2 tspan3 tspan3 tsp-3 tspan4 tspan4 tsp-4, nag-2 tspan5 tspan5 tsp-5 tspan6 tspan6 tsp-6 tspan7 tspan7 cd231/talla-1/a15 tspan8 tspan8 co-029 tspan9 tspan9 net-5 tspan10 tspan10 oculospanin tspan11 tspan11 cd151-like tspan12 tspan12 net-2 tspan13 tspan13 net-6 tspan14 tspan14 tspan15 tspan15 net-7 tspan16 tspan16 tm4-b tspan17 tspan17 tspan18 tspan18 tspan19 tspan19 tspan20 upk1b up1b, upk1b tspan21 tspan21 up1a, upk1a tspan22 prph2 rds, prph2 tspan23 tspan23 rom1 tspan24 cd151 cd151 tspan25 cd53 cd53 tspan26 cd37 cd37 tspan27 cd82 cd82 tspan28 cd81 cd81 tspan29 cd9 cd9 tspan30 cd63 cd63 tspan31 tspan31 sas tspan32 tspan32 tssc6 tspan33 tspan33