title: Thrombin inhibits the pertussis-toxin-dependent ADP-ribosylation of a novel soluble Gi-protein in human platelets.
abstract: A new G-protein was detected in human platelets which was ADP-ribosylated in a pertussis-toxin-dependent manner, was located in the supernatant of saponized platelets and was of a slightly lower molecular mass (40 kDa) than platelet membrane Gi alpha. This soluble ADP-ribosylated protein was immunoprecipitated by an antiserum to Gi alpha, but not by one to Go alpha. Prior thrombin stimulation of platelets led to an inhibition of the ADP-ribosylation of this protein. This inhibition was evident even under conditions which abolished the thrombin-stimulated inhibition of membrane Gi alpha ADP-ribosylation. These results indicate that the platelet thrombin receptor is coupled to two structurally and functionally distinct Gi alpha proteins: a major Gi alpha protein present in platelet membranes, and a minor Gi alpha protein detectable in the platelet soluble fraction.
authors.affiliation: Institut für Prophylaxe und Epidemiologie, Universität München, Federal Republic of Germany.
authors.forename: J M
authors.initials: JM
authors.lastname: Gennity
authors.forename: W
authors.initials: W
authors.lastname: Siess
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000097:blood*; D000818:Animals; D015153:Blotting, Western; D002417:Cattle; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D006801:Humans; D037342:Pertussis Toxin; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D012995:Solubility; D013917:Thrombin / Q000494:pharmacology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
chemical_list: D010975:Platelet Aggregation Inhibitors; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D037342:Pertussis Toxin; D013917:Thrombin; D019204:GTP-Binding Proteins