The
BCR complex
•Ag binding chains – identical to secreted Ig, except for a hydrophobic transmembrane region and a short (3 aa) intracellular motif. (differential. splicing)
• Accessory chains
– Igα and Igβ (necessary for
transport to membrane, signal transduction,
have single Ig fold domain, are disulfide-linked,
and are non-covalently associated).
• Immunoreceptor
tyrosine-based activation motifs
(ITAMs) - Each contain a single ITAM
sequence, consisting of 9-12 residues (used by other receptors in macs, NK cells, etc). Typical motif:
Y X X L/I X6-9 Y X X L\I
Y=tyrosine,
L=leucine, I= isoleucine, X=Any
amino acid (spacing is important for “second
level” kinases, Syk and Zap70)