title: Agonist-selective protection of the opioid receptor-coupled G proteins from inactivation by 5'-p-fluorosulphonylbenzoyl guanosine.
abstract: The guanine nucleotide analogue, 5'-p-fluorosulphonylbenzoyl guanosine (FSBG), can react covalently with GTP-binding proteins (G proteins). In rat brain membranes, FSBG causes a time-dependent loss of beta,gamma-imido[8-3H]guanosine 5'-triphosphate binding sites. Using 1 mM FSBG, the guanyl nucleotide modulation of opioid agonist binding is abolished, whereas the guanyl nucleotide sensitivity of neurotensin binding is retained. The action of FSBG can be prevented by the presence of opioid agonists, but not the antagonist naloxone. Iodoacetamide treatment of membranes in the presence of agonist, but not antagonist, can attenuate the action of FSBG in blocking guanyl nucleotide modulation of opioid agonist binding. These results suggest that FSBG covalently modifies essential thiol groups, whose exposure to the reagent is modified by agonist occupancy of the receptor, on a species of G protein linked to opioid receptors, but not on a species of G protein linked to neurotensin receptors. Thus, FSBG may have selectivity for the forms of Gi or Go, proteins associated with opioid receptors.
authors: MRC Molecular Neurobiology Unit, MRC Centre, Cambridge, England.
authors: Y H
authors: YH
authors: Wong
authors: C D
authors: CD
authors: Demoliou-Mason
authors: M R
authors: MR
authors: Hanley
authors: E A
authors: EA
authors: Barnard
mesh_terms: D000345:Affinity Labels / Q000494:pharmacology*; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D016308:Enkephalin, Leucine-2-Alanine; D004745:Enkephalins / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006151:Guanosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000378:metabolism / Q000494:pharmacology; D007460:Iodoacetamide / Q000494:pharmacology; D007700:Kinetics; D008969:Molecular Sequence Data; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D011957:Receptors, Opioid / Q000187:drug effects / Q000378:metabolism*
chemical_list: C017320:5'-(4-fluorosulfonylbenzoyl)guanosine; D000345:Affinity Labels; D004745:Enkephalins; D011957:Receptors, Opioid; D020875:Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; D006151:Guanosine; D006165:Guanylyl Imidodiphosphate; D009270:Naloxone; D004743:Enkephalin, Leucine; D016308:Enkephalin, Leucine-2-Alanine; D019204:GTP-Binding Proteins; D004229:Dithiothreitol; D007460:Iodoacetamide