CAM KINASE II

(= calcium/calmodulin-dependent kinase II; CaMKII)

A multi-substrate calcium-sensitive kinase composed of four homologous subunits, a, b, g, d, all encoded by different genes. The heteromultimeric holoenzyme (500 - 600kD) has 10 or 12 subunits with the ratio of a,b,g, and d reflecting that present in the cell. Ca2+ /calmodulin-dependent protein kinase II (CaMKII) has been implicated in various neuronal functions, including synaptic plasticity. It is highly concentrated in the postsynaptic region and undergoes autophosphorylation at several sites in a manner that depends on the frequency and duration of Ca2+ spikes. Constitutively active CaMKII produces dendritic exocytosis in the absence of calcium stimulus. CaMKII activation is the primary event leading to inactivation of both CSF (cytostatic factor) and MPF (maturation promoting factor) in mammalian eggs.