title: Oocyte adenylyl cyclase contains Ni, yet the guanine nucleotide-dependent inhibition by progesterone is not sensitive to pertussis toxin.
abstract: Membranes were obtained from Xenopus laevis oocytes after removal of follicular cells by collagenase treatment. [32P]ADP-ribosylation with pertussis toxin showed them to contain a single Mr = 40000 substrate for this toxin that co-migrates on sodium dodecylsufate-polyacrylamide gel electrophoresis with pure human erythrocyte Ni, the inhibitory regulatory component of adenylyl cyclase. [32P]ADP-ribosylation of oocyte membranes with cholera toxin also showed presence of a single substrate but of Mr = 42000. These results indicate, that the adenylyl cyclase system of oocytes, like that of somatic cells and unlike that of spermatozoids, contains the catalytic unit C and both of the known regulatory N components. The possible susceptibility to pertussis toxin of the guanine nucleotide-dependent inhibition of oocyte adenylyl cyclase by progesterone was investigated. This action of progesterone is mediated by a membrane bound receptor as opposed to a receptor of cytosolic or nuclear localization. However, the inhibitory effect of progesterone was unaffected by pertussis toxin, even though the oocyte membrane Ni was fully ADP-ribosylated with pertussis toxin, as revealed by lack of further [32P]ADP-ribosylation on subsequent re-incubation with pertussis toxin. These results indicate that the action of progesterone, in spite of being nucleotide-dependent, is either not mediated by Ni, suggesting the existence of an additional nucleotide regulatory component, or if mediated by Ni, involves a mode of regulation of this coupling protein that is different from that by which all other inhibitory hormones act on adenylyl cyclase.
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D001427:Bacterial Toxins / Q000494:pharmacology*; D002462:Cell Membrane / Q000201:enzymology; D005260:Female; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors*; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D008565:Membrane Proteins / Q000302:isolation & purification; D008970:Molecular Weight; D009865:Oocytes / Q000201:enzymology*; D037342:Pertussis Toxin; D011374:Progesterone / Q000494:pharmacology*; D010566:Virulence Factors, Bordetella; D014981:Xenopus
chemical_list: D037361:Adenylate Cyclase Toxin; D001427:Bacterial Toxins; D008565:Membrane Proteins; D010566:Virulence Factors, Bordetella; D000246:Adenosine Diphosphate Ribose; D006165:Guanylyl Imidodiphosphate; D011374:Progesterone; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases