title: Inhibition by pertussis toxin of guanyl nucleotides exchange on transducin in bovine rod cell membranes.
abstract: The effect of pertussis toxin on GTP-binding protein of bovine rod cell outer segments (transducin) was studied. Pertussis toxin was shown to ADP ribosylate either alpha subunit of free transducin or transducin-GDP complex, whereas GTP and its analogue Gpp(NH)p strongly inhibit ADP ribosylation of transducin. Pertussis toxin inhibits rod outer segment membrane GTPase and GTPase of homogeneous transducin by 40% and 70-80%, respectively. Activation of rod cell cyclic nucleotide phosphodiesterase by transducin is reduced after its preincubation with pertussis toxin. In transducin modified by pertussis toxin, 83% of GDP becomes tightly bound and cannot be exchanged with Gpp(NH)p. The stabilization of complex transducin-GDP after ADP ribosylation can explain the inhibitory effect of pertussis toxin on GTP hydrolysis by transducin, and on phosphodiesterase activation by guanyl nucleotides.
authors.affiliation: Cardiology Research Center of the USSR, Moscow.
authors.forename: V O
authors.initials: VO
authors.lastname: Rybin
authors.forename: A A
authors.initials: AA
authors.lastname: Gureeva
authors.forename: V A
authors.initials: VA
authors.lastname: Tkachuk
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D020558:GTP Phosphohydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006150:Guanine Nucleotides / Q000378:metabolism*; D008027:Light; D037342:Pertussis Toxin; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D010786:Photoreceptor Cells / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000187:drug effects / Q000378:metabolism*; D015293:Transducin / Q000187:drug effects / Q000502:physiology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
chemical_list: D006150:Guanine Nucleotides; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D037342:Pertussis Toxin; D010727:Phosphoric Diester Hydrolases; D020558:GTP Phosphohydrolases; D015293:Transducin