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Mol. Cell. Biol., 05 1995, 2819-2827, Vol 15, No. 5
BL Eide, CW Turck and JA Escobedo
A number of cellular processes, such as proliferation, differentiation, and
transformation, are regulated by cell-extracellular matrix interactions.
Previous studies have identified a novel tyrosine kinase, the focal
adhesion kinase p125FAK, as a component of cell adhesion plaques. p125FAK
was identified as a 125-kDa tyrosine-phosphorylated protein in cells
transformed by the v-src oncogene. p125FAK is an intracellular protein
composed of three domains: a central domain with homology to protein
tyrosine kinases, flanked by two noncatalytic domains of 400 amino acids
which bear no significant homology to previously cloned proteins. p125FAK
is believed to play an important regulatory role in cell adhesion because
it localizes to cell adhesion plaques and because its phosphorylation on
tyrosine residues is regulated by binding of cell surface integrins to the
extracellular matrix. Recent studies have shown that Src, through its SH2
domain, stably associates with pp125FAK and that this association prevents
dephosphorylation of pp125FAK in vitro by protein tyrosine phosphatases. In
this report, we identify Tyr-397 as the primary in vivo and in vitro site
of p125FAK tyrosine phosphorylation and association with Src. Substituting
phenylalanine for tyrosine at position 397 significantly reduces p125FAK
tyrosine phosphorylation and association with Src but does not abolish
p125FAK kinase activity. In addition, p125FAK kinase is able to
trans-phosphorylate Tyr-397 in vitro in a kinase-deficient p125FAK variant.
Phosphorylation of Tyr-397 provides a site [Y(P)AEI] that fits the
consensus sequence for the binding of Src.
Copyright © 1995, American Society for Microbiology
Identification of Tyr-397 as the primary site of tyrosine phosphorylation and pp60src association in the focal adhesion kinase, pp125FAK
Daiichi Research Center, University of California, San Francisco 94143, USA.
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