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

Abstract

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 (C₁‐C₄) and five variable (V₁‐V₅) regions. Although these sequences are highly homologous and closely related to one another V₃‐, V₄‐, and V₅‐regions of γ‐subspecies are slightly bigger than the corresponding regions of the other three subspecies. The first constant region, C₁, contains a tandem repeat of cysteine‐rich sequence (6, total 12 cysteine residues). The third constant region, C₃, 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.