Commentary: The carboxyl-terminal Crk SH3 domain: Regulatory strategies and new perspectives.

Since their discovery as cellular counterparts of viral oncogenes more than two decades ago, enormous progress has been made in unraveling the complex regulatory pathways of signal transduction initiated by the Crk family of proteins. New structural and biochemical studies have uncovered novel insights into both negative and positive regulation of Crk mediated by its atypical carboxyl-terminal SH3 domain (SH3C). Moreover, SH3C is tyrosine phosphorylated by receptor tyrosine kinases and non-receptor tyrosine kinases, thereby permitting assemblages of other SH2/PTB domain containing proteins. Such non-canonical signaling by the Crk SH3C reveals new regulatory strategies for adaptor proteins.