Second
tier of protein kinases-B cells
• Syk (B-cells) and
ZAP-70 (T-cells) represent a second
family of tyrosine kinases that possess two SH2 domains spaced in such a way that they bind to motifs with two phosphotyrosines spaced a precise distance apart, such as those found in ITAMs.
• In B-cells, Syk
binds to the phosphorylated ITAMs of
Igα and Igβ, and as the BCR components cluster, two Syks are brought into contact and phosphorylate each other, activating them.
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