Subcellular distribution of alpha and beta subunit proteins of Ca2+/calmodulin-dependent protein kinase II expressed in Chinese hamster ovary cells.

When two cDNAs respectively encoding the entire coding regions of alpha and beta subunits of Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) were introduced into Chinese hamster ovary cells, the expressed alpha and beta subunits were differently associated with subcellular structure. Although alpha subunit was loosely associated with subcellular structure, about 80% of CaM kinase II activity of alpha subunit was found in soluble fraction. More than 50% of the beta subunit bound to the membrane, and the remainder was soluble but was loosely associated with subcellular structure. The relative rate of phosphorylation for substrate proteins of the beta subunit bound to membrane was significantly different from that of the soluble form.