title: Effect of Al3+ plus F- on the catecholamine-stimulated GTPase activity of purified and reconstituted Gs.
abstract: The effects of Al3+ and F- on the catecholamine-stimulated GTPase cycle were studied by using reconstituted phospholipid vesicles that contained purified beta-adrenergic receptor and the stimulatory GTP-binding protein of the adenylate cyclase system, Gs. Al3+/F- activated reconstituted Gs to levels previously reported for detergent-solubilized, purified Gs, although both activation and deactivation were faster in the reconstituted preparation. Under these conditions, Al3+/F- did not inhibit by more than 15% the beta-adrenergic agonist-stimulated GTPase activity of the vesicles nor did it significantly inhibit the rates of GTP binding, GTP hydrolysis, or GDP release. When Mg2+ (50 mM) was used instead of agonist to promote GTP hydrolysis in the receptor-Gs vesicles, Al3+/F- was found to inhibit GTP gamma S binding, GDP release, and steady-state GTPase activity to unstimulated levels. These data can be interpreted as indicating that the receptor catalyzes nucleotide exchange by Gs faster or more efficiently than does Mg2+.
mesh_terms: D000535:Aluminum / Q000494:pharmacology*; D000818:Animals; D002395:Catecholamines / Q000494:pharmacology*; D005459:Fluorides / Q000494:pharmacology*; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010761:Phosphorus Radioisotopes; D011817:Rabbits; D013873:Thionucleotides / Q000378:metabolism
chemical_list: D002395:Catecholamines; D010761:Phosphorus Radioisotopes; D013873:Thionucleotides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D000535:Aluminum; D010744:Phosphoric Monoester Hydrolases; D020558:GTP Phosphohydrolases; D005459:Fluorides