title: The effect of activating ligands on the intrinsic fluorescence of guanine nucleotide-binding regulatory proteins.
abstract: The intensity of the tryptophan fluorescence of the alpha subunits of guanine nucleotide-binding regulatory proteins increases when they bind guanosine 5'-O-(3-thio)triphosphate (GTY gamma S). The kinetics of the fluorescence enhancement and of the measured binding of [35S]GTP gamma S are well correlated. The addition of Mg2+ to the nucleotide-bound proteins causes a further, rapid increase in the fluorescence intensity. Similar effects result from exposure of the proteins to F- and Mg2+, and the required concentration of F- is reduced by the inclusion of Al3+. It is presumed that the more highly fluorescent state of the G protein alpha subunits represents their active conformation.
mesh_terms: D000535:Aluminum / Q000494:pharmacology; D000077410:Aluminum Chloride; D017607:Aluminum Compounds; D000818:Animals; D002712:Chlorides / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D008099:Liver / Q000378:metabolism; D008278:Magnesium Sulfate / Q000494:pharmacology; D011485:Protein Binding; D011817:Rabbits; D012969:Sodium Fluoride / Q000494:pharmacology; D013050:Spectrometry, Fluorescence / Q000379:methods; D013873:Thionucleotides / Q000378:metabolism*
chemical_list: D017607:Aluminum Compounds; D002712:Chlorides; D008024:Ligands; D013873:Thionucleotides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D000077410:Aluminum Chloride; D008278:Magnesium Sulfate; D006160:Guanosine Triphosphate; D012969:Sodium Fluoride; D000535:Aluminum; D019204:GTP-Binding Proteins