Crk-proteine

Crk, also known as proto-oncogene c-Crk, is a protein (adapter protein) that in humans is encoded by the CRK gene. The CRK protein is involved in the reelin signaling cascade downstream of DAB1. The name Crk comes from "CT10 Regulator of Kinase", CT10 being the avian virus from which a protein was isolated. This protein lacks kinase domains but is able to stimulate the phosphorylation of tyrosines in cells.

Crk is a member of an adaptor protein family that binds to several tyrosine phosphorylated proteins. Crk has multiple SH2 and SH3 domains(src homology domains) and is involved in several signaling pathways. It recruits cytoplasmic proteins near the tyrosine kinase through SH2-phosphotyrosine interaction. The N-terminal SH2 domain of this protein acts as a positive regulator of transformation, whereas the C-terminal SH3 domain acts as a negative regulator of transformation. Two alternative transcripts encoding different isoforms with different biological activities have been described.

V-Crk, a transforming oncoprotein from avian sarcoma viruses, is a fusion of the viral "gag" protein with the SH2 and SH3 domains of cellular Crk.