title: Isolation and purification of a small-molecular-weight GTP-binding protein from plants.
abstract: As part of testing the hypothesis that signal transduction in higher plants is mediated by G-protein(s), a 24-kDa GTP-binding protein was isolated and purified to near homogeneity from 3.5-day-old dark grown oat (Avena) seedlings by hydroxyapatite, GTP-agarose, and Sephacryl S-200 chromatographies. The protein bound maximally 0.9 +/- 0.1 mol of [35S]guanosine 5'-(3-O-thio) triphosphate (GTP gamma S)/mol of protein with an apparent Kd of approximately 32 nM. Although binding of [35S]GTP gamma S was inhibited by both GTP and GDP, no inhibition of [35S]GTP gamma S binding was observed in the presence of ATP, UTP, CTP, ITP, or TTP. The 24-kDa protein hydrolyzed GTP with a rate of 0.06 mol Pi/mol protein/min. The results suggest that this GTP-binding protein is a unique plant GTP-binding protein that exhibits characteristics similar to those of animal ras-related GTP-binding proteins.
authors.affiliation: Department of Chemistry, University of Nebraska-Lincoln 68588-0304.
authors.forename: D
authors.initials: D
authors.lastname: Sommer
authors.forename: P S
authors.initials: PS
authors.lastname: Song
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D018554:Avena / Q000737:chemistry*; D001667:Binding, Competitive; D002772:Cholera Toxin / Q000378:metabolism; D002846:Chromatography, Affinity; D003429:Cross Reactions; D003624:Darkness; D005033:Ethylmaleimide / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000032:analysis; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives; D008970:Molecular Weight; D012685:Sepharose / Q000031:analogs & derivatives; D015398:Signal Transduction; D018631:ras Proteins / Q000187:drug effects / Q000302:isolation & purification*
chemical_list: C068914:guanosine triphosphate-agarose; D000246:Adenosine Diphosphate Ribose; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D006160:Guanosine Triphosphate; D012685:Sepharose; D002772:Cholera Toxin; D020558:GTP Phosphohydrolases; D018631:ras Proteins; D005033:Ethylmaleimide