title: Calmodulin triggers the resumption of meiosis in amphibian oocytes.
abstract: The calcium-binding protein, calmodulin, has been purified from Xenopus laevis oocytes. This 18,500-dalton protein, pl 4.3, has two high-affinity calcium-binding sites per mole protein having a dissociation constant of 2.8 x 10(-6) M. Full-grown Xenopus oocytes, arrested in late G2 of the meiotic cell cycle, resumed meiosis when microinjected with 60-80 ng (3-4 pmol) of calmodulin in the form of a calcium-calmodulin complex. The timing of the meiotic events in these recipient oocytes was the same as that normally induced by progesterone. Xenopus ovarian calmodulin stimulated bovine brain phosphodiesterase (PDE) 3- to 10-fold in a calcium-dependent manner, but it had no apparent effect on ovarian PDE activity. A calcium-calmodulin-dependent protein kinase has been isolated from Xenopus oocytes using a calmodulin-Sepharose 4B affinity column. The possible role for this kinase in regulating the G2-M transition in oocytes has been discussed.
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology*; D002846:Chromatography, Affinity; D005260:Female; D008540:Meiosis / Q000187:drug effects*; D009865:Oocytes / Q000187:drug effects* / Q000201:enzymology; D010063:Ovum / Q000187:drug effects*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D011494:Protein Kinases / Q000302:isolation & purification; D014982:Xenopus laevis
chemical_list: D002135:Calcium-Binding Proteins; D002147:Calmodulin; D011494:Protein Kinases; D010727:Phosphoric Diester Hydrolases