Structure and developmental regulation of the murine ctk gene

Csk-type protein tyrosine kinase (Ctk) is a protein tyrosine kinase with structural and functional similarities to C-terminal Src kinase (Csk). These enzymes catalyze the phosphorylation of C-terminal regulatory tyrosine residues of Src family enzymes. Here we describe the structure of the ctk gene and characterize the pattern of ctk expression. Ctk and a closely related enzyme, nervous tissue and T-lymphocyte kinase (Ntk), are assembled by selective use of two of the exons. Expression of ctk was found to be restricted primarily to the brain, ctk and csk exhibit a different expression profile in the developing mouse brain. The expression of the ctk mRNA and mature polypeptide increase postnatally, while the expression of csk decreases with age. Our results thus show that despite their structural and functional similarities, ctk and csk differ markedly in their patterns of expression.