Protein kinase C--structural studies.

Abstract

Protein kinase C was first reported by Nishizuka and colleagues. This group identified a histone kinase activity that was irreversibly activated by mM concentrations of Ca2+ (Takai et al., 1977), an effect shown to be due to proteolysis of the holoenzyme by contaminating Ca2+-activated neutral protease (Inoue et al., 1977). Reversible activation was subsequently shown to occur in response to Ca2+ (~10-5M) and anionic phospholipid, phosphatidylserine being the most effective (Takai et al., 1979). Furthermore, activation could be effected at physiological Ca2+ concentrations (~10-6M) if the neutral lipid diacylglycerol was also present (Kishimoto et al., 1980). These characteristics of protein kinase C have led to the operational definition of the enzyme as a Ca2+/phospholipid dependent protein kinase.