Cd79a
Domain
The transmembrane helices of CD79A and CD79B chains and two IgM heavy chains assembly in a four-helix bundle structure that appears to be conserved among different BCR isotypes.
Function
Required in cooperation with CD79B for initiation of the signal transduction cascade activated by binding of antigen to the B-cell antigen receptor complex (BCR) which leads to internalization of the complex, trafficking to late endosomes and antigen presentation. Also required for BCR surface expression and for efficient differentiation of pro- and pre-B-cells. Stimulates SYK autophosphorylation and activation. Binds to BLNK, bringing BLNK into proximity with SYK and allowing SYK to phosphorylate BLNK. Also interacts with and increases activity of some Src-family tyrosine kinases. Represses BCR signaling during development of immature B-cells.
Post-translational modifications
Phosphorylated on tyrosine, serine and threonine residues upon B-cell activation. Phosphorylation of tyrosine residues by Src-family kinases, including LYN, is an early and essential feature of the BCR signaling cascade. The phosphorylated tyrosines serve as docking sites for SH2-domain containing kinases, leading to their activation which in turn leads to phosphorylation of downstream targets. Phosphorylation of serine and threonine residues may prevent subsequent tyrosine phosphorylation.
Arginine methylation in the ITAM domain may interfere with the binding of SYK. It promotes signals leading to B-cell differentiation.
Tissue Specificity
B-cells.
Cellular localization
- Cell membrane
- Single-pass type I membrane protein
- Following antigen binding, the BCR has been shown to translocate from detergent-soluble regions of the cell membrane to lipid rafts although signal transduction through the complex can also occur outside lipid rafts.
Alternative names
CD79a, Iga, Mb-1, Cd79a, B-cell antigen receptor complex-associated protein alpha chain, Ig-alpha, MB-1 membrane glycoprotein, Membrane-bound immunoglobulin-associated protein, Surface IgM-associated protein