title: Microinjection of a 19-kDa guanine nucleotide-binding protein inhibits maturation of Xenopus oocytes.
abstract: ADP-ribosylation factors (ARFs) are 19-21-kDa proteins purified from bovine brain that bind guanosine 5'-triphosphate (GTP). They exhibit GTP-dependent activity as activators of cholera toxin-catalyzed ADP-ribosylation of the alpha-subunit of the stimulatory guanine nucleotide-binding protein of the adenylyl cyclase system (Gs alpha). ARF, which interacts directly with the catalytic subunit of cholera toxin, has no known physiologic role. Intracellular microinjection of ARF was employed to investigate the effect of ARF on progesterone- and insulin-stimulated maturation of Xenopus oocytes. Maturation was inhibited by injection of ARF 3-8 h before exposure of oocytes to progesterone or insulin. ARF inhibition was dependent on progesterone concentration but not on insulin concentration. Inhibition was enhanced by concomitant injection of GTP and to a greater extent by guanosine 5'-O-(thiotriphosphate) (GTP gamma S) which, in the absence of ARF, inhibited somewhat at early time points. The demonstration of this effect of ARF on both progesterone- and insulin-stimulated oocyte maturation may provide a clue to the physiologic role of this guanine nucleotide-binding protein.
authors.affiliation: Laboratory of Cellular Metabolism, National Heart, Lung, and Blood Institute, Bethesda, Maryland 20892.
authors.forename: T D
authors.initials: TD
authors.lastname: Bahnson
authors.forename: S C
authors.initials: SC
authors.lastname: Tsai
authors.forename: R
authors.initials: R
authors.lastname: Adamik
authors.forename: J
authors.initials: J
authors.lastname: Moss
authors.forename: M
authors.initials: M
authors.lastname: Vaughan
mesh_terms: D020727:ADP-Ribosylation Factors; D000818:Animals; D005260:Female; D019204:GTP-Binding Proteins / Q000032:analysis / Q000494:pharmacology*; D006131:Growth Inhibitors / Q000494:pharmacology*; D006153:Guanosine Diphosphate / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D007328:Insulin / Q000494:pharmacology; D008565:Membrane Proteins / Q000032:analysis / Q000494:pharmacology*; D008845:Microinjections; D008970:Molecular Weight; D009865:Oocytes / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology; D009866:Oogenesis / Q000187:drug effects*; D011374:Progesterone / Q000494:pharmacology; D013997:Time Factors; D014982:Xenopus laevis
chemical_list: D006131:Growth Inhibitors; D007328:Insulin; D008565:Membrane Proteins; D006153:Guanosine Diphosphate; D011374:Progesterone; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D020727:ADP-Ribosylation Factors