Bovine Brain Coated Vesicles Contain Guanine Nucleotide Regulatory Proteins

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 1 μΜ of GTP, guanosine diphosphate and guanosine 5’-(3-0-thio)triphosphate. Incubation of the vesicles with islet-activating protein and p’PJNAD 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.