Production and characterization of an antibody specific for a novel protein serine threonine kinase, MPK38, highly expressed in hematopoietic cells

We report an antibody that selectively recognizes MPK38, a new protein seri ne/threonine kinase closely related to the SNF1 serine/threonine kinase fam ily. This antibody recognized a region of the N-terminal kinase catalytic d omain and part of the remaining C-terminal portion and was sensitive enough to detect a 72-kDa recombinant MPK38 in insect cells by Western blotting. Immunoblot analysis showed that the recombinant MPK38 was expressed in a ti me-dependent manner and reached a maximum after 48 h postinfection. In addi tion, the immune complex kinase assay revealed that the recombinant and end ogenous MPK38 protein autophosphorylated in vitro. Phosphoamino acid analys is of autophosphorylated MPK38 protein showed that the phosphorylation was exclusively on serine and threonine residues, suggesting that MPK38 is a pr otein serine/threonine kinase. Thus, this antibody could be helpful for elu cidating the biological functions of MPK38 in the MPK38-expressing cells.