Purification of GTP-binding proteins from bovine brain membranes Identification of heterogeneity of the α-subunit of Go proteins

AbstractUsing high-resolution Mono Q column chromatography, we purified 6 distinct peaks of GTP-binding proteins from bovine brain membranes. Five of them consisted of 3 polypeptides with αβγ-subunits and served as the substrate of islet-activating protein (IAP), pertussis toxin. The other one was purified as α-subunit alone and was also ADP-ribosylated by IAP in the presence of βγ-subunits. When each α-subunit was characterized by immunoblot analysis using various antibodies with defined specificity, the two of them were identified as gi-1 and Gi-2, and other 4 appeared to be Go or Go-like G proteins. The α-subunits of immunologically Go-like proteins were apparently distinguishable from one another on elution profiles from the Mono Q column. Thus, there was a heterogeneity of the α-subunit of Go in the brain membranes.ADP-ribosylation; GTP-binding protein; Islet-activating protei