The common structure and activities of four subspecies of rat brain protein kinase C family

Elucidation of the complete sequences of four cDNA clones (α, βI, βII, and γ) of the rat brain protein kinase C family has revealed their common structure composed of a single polypeptide chain with four constant (C 1-C 4) and five variable (V 1-V 5) regions. Although these sequences are highly homologous and closely related to one another V 3-, V 4-, and V 5-regions of γ-subspecies are slightly bigger than the corresponding regions of the other three subspecies. The first constant region, C 1, contains a tandem repeat of cysteine-rich sequence (6, total 12 cysteine residues). The third constant region, C 3, has an ATP-binding sequence which is found in many protein kinases. In adult rat whole brain, the relative activities of α-, βI, βII, and γ-subspecies are roughly 16, 8, 55, and 21%, respectively. γ-Subspecies is expressed after birth apparently only in the central nervous tissue, implying its role in the regulation of specific neuronal functions.