CSK-homologous kinase (CHK), a protein kinase that displays significant sequence similarity with CSK. Depending on its structural features and the origins of the cDNA libraries, CHK was also named Hyl, BatK, Matk, Ctk and Ntk. Both CSK and CHK are cytosolic protein tyrosine kinases. Membrane translocation of CHK is mainly mediated by binding to membrane proteins and signaling adaptor proteins via their SH2, SH3 and/or kinase domains CHK is recruited to the plasma membrane by binding to membrane proteins ErbB2, c-Kit, and TrkA via its SH2 domain. Deletion of the SH3 domain abolishes the abilities of CHK to anchor to the plasma membrane to inhibit Lyn, and to suppress cell spreading. Mutation of Ser-78 in the SH3 –SH2 connector of CHK resulted in a significant loss of activity. CHK may perform unique functions in the nucleus and these functions are related to the ability of CHK to suppress myeloid cell growth.


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