Presence of phospholipase C in coated vesicles from bovine brain. Dual regulatory effects of GTP-analogs.

Bovine brain coated vesicles display free calcium-dependent phospholipase C activity. Gpp(NH)p and GTP gamma S inhibited phospholipase C at nanomolar concentrations. Increasing concentrations of Gpp(NH)p and GTP gamma S reversed the inhibitory effects and stimulated phospholipase C activity. Preincubation of coated vesicles with pertussis toxin blocked the poorly-hydrolyzable GTP-analogs' inhibitory effects on phospholipase C. These data indicate that guanine nucleotides exert a dual regulatory control of phospholipase C in coated vesicles and that the inhibitory pathway is mediated by a pertussis toxin-sensitive G-protein.