Adapter molecule crk is a member of an
adapter protein family that binds to several tyrosine-phosphorylated proteins. This protein has several
SH2 and
SH3 domains (src-homology domains) and is involved in several signaling pathways, recruiting cytoplasmic proteins in the vicinity of
tyrosine kinase through SH2-phosphotyrosine interaction. The
N-terminal SH2 domain of this protein functions as a positive regulator of transformation whereas the
C-terminal SH3 domain functions as a negative regulator of transformation. Two alternative transcripts encoding different isoforms with distinct biological activity have been described. Crk together with
CrkL participates in the
Reelin signaling cascade downstream of
DAB1. The name Crk is from "CT10 Regulator of Kinase" where CT10 is the avian virus from which was isolated a protein, lacking kinase domains, but capable of stimulating phosphorylation of tyrosines in cells. Crk should not be confused with
Src, which also has cellular (c-Src) and viral (v-Src) forms and is involved in some of the same signaling pathways but is a protein tyrosine-kinase. ==Interactions==