CRK belongs to the signaling adapter protein family which binds to several tyrosine-phosphorylated proteins. CRK is involved in many cellular processes such as apoptosis， proliferation， and differentiation. CRK has a modular domain architecture consisting of an SH2 followed by two SH3 domains （src-homology domains）. The N-terminal SH2 domain of the CRK protein functions as a positive regulator of transformation whereas the C-terminal SH3 domain functions as a negative regulator of transformation.
