Interaction of substance P, compound 48/80 and mastoparan with the alpha-subunit C-terminus of G protein.

Pretreatment of purified calf brain G proteins with activated pertussis toxin or antibodies raised against the C-terminus of their alpha subunits prevented the increase in GTPase activity induced by substance P, compound 48/80 and mastoparan. These results suggest that these mast cell secretagogues activate G proteins directly via an interaction with the C-terminus of alpha subunits of G proteins by mimicking the agonist-liganded receptors.