Characterization of G-proteins in rat glomeruli

G-proteins in rat glomeruli were examined using bacterial toxin-catalyzed ADP-ribosylation and specific immunoblots. ADP-ribosylation catalyzed by cholera and pertussis toxin demonstrated the existence of Gs and Gi proteins in the glomerular membranes. Immunoblots further revealed two types of Gs alpha (45 and 52 kDa), Gi alpha 1 and/or Gi alpha 2 (40-41 kDa), Gi alpha 3 (40 kDa) and G beta (35-36 kDa) but not Go alpha in the membranes of the glomeruli. The predominant subspecies of Gs alpha was a 52 kDa protein. However, detectable amounts of G-proteins did not exist in cytosolic extracts of the glomeruli. We conclude that several subspecies of Gs and Gi proteins are present in rat glomerular membranes.