Ca2+/calmodulin-dependent protein kinases from the neuronal nuclear matrix and post-synaptic density are structurally related.

A major Ca2+/calmodulin-dependent protein kinase has been isolated in association with the neuronal nuclear matrix. Nuclear matrix preparations contain highly phosphorylated polypeptides with Mr values of 50,000 and 60,000. These polypeptides were further characterized by peptide and phospho peptide mapping, two-dimensional isoelectrofocusing/NaDodSO4/PAGE, and 125I-labeled calmodulin binding. The results indicate that the Mr 50,000 and 60,000 polypeptides of the nuclear matrix closely resemble the alpha and beta subunits, respectively, of the Ca2+/calmodulin-dependent protein kinase of the post-synaptic density. These findings indicate that similar protein kinases mediate the neuronal effects of Ca2+ at the cytosolic, synaptosomal, and nuclear levels.