Lck

Lck or leukocyte-specific protein tyrosine kinase is a protein tyrosine kinase, associated with the cytoplasmictails of CD4or CD8co-receptor. When a TCR:CD3:MHCcomplex has formed, it phosphorylates CD3? and ? with help of Fyn, allowing ZAP-70, a cytoplasmic protein tyrosine kinase, to bind this complex. Lck can then phosphorylate and activate ZAP-70 itself too. ZAP-70 is an important signaling protein which eventually activates transcription factors as NF?B, which induces cell proliferation and differentiation.
Lck is inhibited by CBL, which is part of the ubiquitin mediated pathway.

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It uses material from the http://en.wikipedia.org/wiki/Lck Wikipedia article Lck.