Ca²⁺ -calmodulin-dependent protein kinase in neuronal nuclei

Ca²⁺ -calmodulin-dependent protein kinase represents a major enzyme activity in neuronal nuclei. Most of the protein kinase activity is associated with the nuclear matrix but it can phosphorylate a broad range of substrates which derive from different nuclear compartments. Notable among these substrates is a M(r) = 50,000 component of the nuclear matrix and a high mobility group chromatin protein which behaves like HMG17. The high level of activity, age- and tissue-specificity, and sensitivity to low concentrations of calmodulin suggest a role for this Ca²⁺-calmodulin-dependent protein kinase in regulating a neuronal function at the level of the nucleus.