Expressed on the membrane of immature thymocytes.
Consits of the invariant surrogate α chain, pTα , a 33 kDa glycoprotein (gp 33) disulphide-linked to a TcR β chain , and associated with the CD3 proteins.
Unlike the pre-BcR surrogate light chain which comprises the Vpre-B and the λ -like polypeptides non bound to the membrane, the pTα chain is a type I transmembrane protein whose cytoplasmic tail contains two potential phosphorylation sites and a Src homology 3 (SH3)-domain binding sequence .
A signal through the pre-TcR complex is required for cell survival and for proper transition from the DN to DP stage .
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