Nucleotide sequence of a cDNA coding for rat hck tyrosine kinase and characterization of its gene product

Abstract

The hck gene is member of src family of non-receptor type tyrosine kinases. Here we report the nucleotide sequence of the rat hck eDNA of 1.94 kb. The nuclcotide sequence shows an open reading frame coding for a polypeptide of 503 amino acids. A vector expressing a fusion protein of glutathione-S-transferase with 82 amino acids of the N-terminal region of hck (from amino acids 32 to 113) was constructed, Using this bacterially expressed fusion protein antibodies were prepared which recognize the cellular hck gene product. These antibodies identified, by immunoblotting, two polypeptides of 56 and 59 kDa in rat spleen where hck transcripts are present at high level. Immunoprecipitated hck polypeptides were enzymatically active and were autophosphorylated in the presence of ATP and Mg²⁺. 1mmunoprecipitated hck could phosphorylate exogenous substrates. Treatment of immunoprecipitated hck by a purified protein tyrosine phosphatase decreased its enzymatic acitivity. Our results suggest that the enzymatic activity of hck tyrosine kinase is regulated by phosphorylation and dephosphorylation.