title: Photoaffinity identification of colchicine-solubilized regulatory subunit from rat brain adenylate cyclase.
abstract: Five GTP binding proteins in rat cerebral cortex synaptic membranes were identified by photoaffinity labelling with [3H] or [32P](P3-azido-anilido)-P1-5' GTP (AAGTP). When AAGTP-treated membranes were incubated with colchicine or vinblastine and subsequently washed, a single AAGTP-labelled protein of 42 kD was released into the supernatant. About 30% of the total labelled 42-kD protein was released into supernatants from membranes pretreated with colchicine or vinblastine compared with 15% released from control membranes. The amount of adenylate cyclase regulatory subunit (G unit) remaining in these membranes was assessed with reconstitution studies after inactivating the adenylate cyclase catalytic moiety with N-ethylmaleimide (NEM). Forty to fifty percent of functional G units were lost from membranes treated with colchicine prior to washing. This 40-50% loss of functional G unit after colchicine treatment corresponds to the previously observed 42% loss of NaF and guanylyl-5'-imidodiphosphate [Gpp(NH)p]-activated adenylate cyclase. Release of the AAGTP-labelled 42-kD protein from colchicine-treated synaptic membranes is double that from lumicolchicine-treated membranes. This colchicine-mediated release of 42-kD protein correlates with a doubling of functional G unit released from synaptic membranes after colchicine treatment. These findings suggest multiple populations of the G unit within the synaptic plasma membrane, some of which may interact with cytoskeletal components.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000345:Affinity Labels / Q000378:metabolism; D000818:Animals; D001386:Azides / Q000378:metabolism*; D001921:Brain / Q000187:drug effects / Q000201:enzymology*; D003078:Colchicine / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005033:Ethylmaleimide / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013570:Synaptic Membranes / Q000201:enzymology; D014747:Vinblastine / Q000494:pharmacology
chemical_list: D000345:Affinity Labels; D001386:Azides; D006165:Guanylyl Imidodiphosphate; D014747:Vinblastine; C031907:GTP gamma-4-azidoanilide; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D005033:Ethylmaleimide; D003078:Colchicine