title: Kinetic analysis of the binding of guanine nucleotide to bovine brain smg p25A.
abstract: Bovine brain smg p25A, a guanine nucleotide-binding protein with a Mr of about 25,000, bound specifically GTP, guanosine 5'-(3-O-thio)triphosphate (GTP gamma S) and GDP. The initial velocities of the binding of GTP gamma S to GDP-bound smg p25A and the dissociation of GDP from this protein increased by decreasing Mg2+ concentrations or increasing NaCl concentrations. The initial velocity of the binding of GTP gamma S to GDP-free smg p25A was not affected by changing Mg2+ concentrations. These results indicate that the dissociation of GDP from smg p25A limits the binding of GTP to this protein, and suggest that there is a protein stimulating the dissociation of GDP from smg p25A and thereby stimulating the binding of GTP to this protein in mammalian tissues. In fact, the protein stimulating the dissociation of GDP, but not of GTP gamma S, from smg p25A was detected in bovine brain cytosol.
authors.affiliation: Department of Biochemistry, Kobe University School of Medicine, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Shoji
authors.forename: A
authors.initials: A
authors.lastname: Kikuchi
authors.forename: S
authors.initials: S
authors.lastname: Kuroda
authors.forename: Y
authors.initials: Y
authors.lastname: Takai
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D002417:Cattle; D003600:Cytosol / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006150:Guanine Nucleotides / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000031:analogs & derivatives*; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology; D013462:Sulfur Radioisotopes; D013873:Thionucleotides / Q000378:metabolism
chemical_list: D006150:Guanine Nucleotides; D009419:Nerve Tissue Proteins; D013462:Sulfur Radioisotopes; D013873:Thionucleotides; C034882:guanosine 5'-O-(1-thiotriphosphate); D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D012965:Sodium Chloride; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D008274:Magnesium