Purification and properties of the inhibitory guanine nucleotide regulatory unit of brain adenylate cyclase.

摘要: Hormonal inhibition of adenylate cyclase is mediated by a guanine nucleotide regulatory protein (Ni) which different from the one mediates hormonal stimulation. There substantial evidence that active component Ni (termed alpha i can be ADP-ribosylated toxin Bordetella pertussis. We have found in bovine cerebral cortex there are three proteins similar molecular weight (39,000-41,000) modified pertussis toxin. purified these and resolved 41,000-dalton 40,000/39,000-dalton doublet. All forms substrate isolated free form or together with 36,000 beta component. also this ADP-ribosylation substrates greatly enhanced addition This makes possible an assay subunit activity based on its interaction i. The we differ two functions: susceptibility to GTPase activity. more readily than smaller forms. 39,000-dalton has low Km (0.3 microM) for GTP. doubled phospholipids. almost undetectable. It not yet known what relationship each other. may derived larger proteolysis it intrinsically different. remains shown whether represents type transmits signal effectors other cyclase.