Crk II (Tyr-251), Phosphospecific Antibody

The Crk family of adaptor proteins (Crk I, Crk II and CrkL) are Src Homology 2 (SH2) and Src Homology 3 (SH3) domain-containing proteins that form protein complexes important for transmiting signals downstream of tyrosine kinases. Both Crk II and CrkL are composed of a single SH2 domain, followed by two tandem SH3 domains. Crk II is also alternatively spliced to a minor product, Crk I, which is structurally and functionally more similar to the v-Crk oncogene. Both Crk II and CrkL are ubiquitously expressed and their SH domains are highly homologous, however both are required for mouse development and have distinct non-overlapping phenotypes in knockout mice. Phosphorylation may be important for regulating Crk activity. Crk II Tyr-221 (CrkL Tyr-207) phosphorylation is a negative regulatory site, while Crk Tyr-251 phosphorylation in the SH3 domain is a positive regulatory site. EGF stimulation induces phosphorylation of Tyr-251, which increases binding of Crk to the SH2 domain of Abl, and promotes transactivation of Abl.

The antibody detects a 38 and 40 kDa* proteins corresponding to the molecular mass of Crk II and CrkL on SDS-PAGE immunoblots of human K562 cells stimulated with pervanadate and A431 cells stimulated with EGF. This reactivity is not observed after akaline phosphatase treatment. This peptide sequence is well conserved in mouse and rat Crk II, as well as in CrkL (Tyr-251) . The site is not found in Crk I.