G-proteins in rat blood vessels--I. Identification

1. The purpose of this investigation was to identify various types of conventional, low and high molecular weight G-proteins in purified membranes of rat aorta and mesenteric artery. 2. In both blood vessels, immunoblotting of G-proteins using AS/7 antibody specific for Gi-1/2, EC/2 antibody specific for Gi-3 and RM/1 antibody specific for Gs-type conventional G-proteins demonstrated the presence of M(r) 28-43 kDa, M(r) 41 and 48 kDa, and M(r) 36-46 kDa polypeptides, respectively. Immunoblotting using a common antibody (GA/1) for the Gs and Gi alpha-subunits also revealed the existence of multiple polypeptides (M(r) 24-52 kDa) in both aorta and mesenteric artery, some of which were identified by the specific antibodies. The intensity and number of bands detected by most of the antibodies were greater in mesenteric artery than in aorta. 3. Cholera toxin (CT) catalyzed ADP-ribosylation of two Gs alpha (M(r) 43, 46 kDa) in both types of blood vessels with similar intensities of bands. Pertussis toxin (PT), on the other hand, catalyzed ADP-ribosylation of one Gi alpha (M(r) 41 kDa) polypeptide, and the intensity of this band was greater in aorta than in mesenteric artery. The polypeptides ADP-ribosylated by the toxins corresponded with their identification by antibodies. 4. Nitrocellulose blot overlay with [35S]GTP gamma S identified at least seven low molecular weight G-proteins (M(r) 21-30 kDa) in both aorta and mesenteric artery, with greater intensity of bands in mesenteric artery.(ABSTRACT TRUNCATED AT 250 WORDS)