Calmodulin-dependent protein kinase IV (CaM-kinase IV) is a Ca(2+)-responsive multifunctional protein kinase which occurs abundantly in the brain and thymus. A human cDNA clone encoding CaM-kinase IV was isolated from a Jurkat cell cDNA library and its nucleotide sequence was determined. The cDNA sequence encoded a protein consisting of 473 amino acids with a molecular weight of 51,925. The nucleotide sequence for the coding region and the deduced amino acid sequence showed 81 and 80% identities with those of the rat enzyme, respectively. Western blot analysis, using a polyclonal antibody raised against the recombinant human CaM-kinase IV, which was expressed in Escherichia coli, revealed two bands corresponding in mobility to molecular weights of 60,000 and 61,000, respectively, in a Jurkat cell extract. The antibody also cross-reacted with both isoforms of CaM-kinase IV from rat cerebellum, the apparent molecular weights being 62,000 and 64,000, respectively.