title: The influence of bound GDP on the kinetics of guanine nucleotide binding to G proteins.
abstract: Purified guanine nucleotide-binding regulatory proteins, as either the oligomers or the isolated nucleotide-binding alpha subunits, display anomalous kinetics of nucleotide binding. This is due to the presence of tightly bound GDP in these preparations. The dissociation of bound GDP is the rate-limiting step for nucleotide binding. GDP can be removed by chromatography in the presence of 1 M (NH4)2SO4 and 20% glycerol, which yields preparations of G proteins that contain less than 0.1 mol of GDP/mol of guanosine 5'-(gamma-thio)triphosphate (GTP gamma S)-binding site. When the GDP is removed, the binding of GTP gamma S displays kinetics consistent with a bimolecular reaction.
mesh_terms: D000645:Ammonium Sulfate / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000032:analysis / Q000378:metabolism*; D005990:Glycerol / Q000494:pharmacology; D006150:Guanine Nucleotides / Q000032:analysis* / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006153:Guanosine Diphosphate / Q000032:analysis* / Q000302:isolation & purification; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D007700:Kinetics; D013873:Thionucleotides / Q000378:metabolism
chemical_list: D006150:Guanine Nucleotides; D013873:Thionucleotides; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D005990:Glycerol; D000645:Ammonium Sulfate