CLONING, EXPRESSION ANALYSIS, AND FUNCTIONAL-CHARACTERIZATION OF PKL12, A MEMBER OF A NEW SUBFAMILY OF SER THR KINASES/

We report the cloning of the full-length cDNA of a new murine protein kinase, mPKL12. The sequence reveals a 305-amino-acid protein that con tains the characteristic subdomains of the kinase superfamily and part icular homology indicating a ser/thr specificity. We have also identif ied its human homologue gene (94% identical) and the putative homologu e proteins from Saccharomyces cerevisiae and Arabidoposis thaliana. Th ese four sequences appear to form a new subfamily of protein kinases, close in size to the theoretical minimal catalytic domain, therefore s uggesting that they could be the catalytic unit of a more complex holo enzyme. Using Escherichia coli-purified protein, we have demonstrated that the mPKL12 enzyme possesses an intrinsic kinase activity, capable of phosphorylating enolase and also of promoting autophosphorylation, with a ser/thr specificity. Tissue expression analysis of mPKL12 show ed that it is ubiquitously expressed, although at very low levels. RT- PCR analysis of several cell lines also supports this view, therefore suggesting that PKL12 may play a role in a very general cellular funct ion, probably related with the secretory pathway. (C) 1998 Academic Pr ess.