Abstract
Binding of [3H]guanosine triphosphate (GTP) with a high affinity was found to be present in the coated vesicle fraction prepared from bovine cerebral cortex. The binding was saturable and displaced by 1μM of GTP, guanosine diphosphate and guanosine 5'-(3-O-thio)triphosphate. Incubation of the vesicles with islet-activating protein and [32P]NAD resulted in ADP-ribosylation of a 39, 000—41, 000-dalton polypeptide. Antibodies to the α-subunit of stimulatory guanine nucleotide regulatory proteins (G-proteins) immunoblotted 52, 000 and 45, 000-dalton polypeptides. The results indicate that stimulatory and inhibitory G-proteins are contained in a fraction of the bovine brain coated vesicles.
