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Calmodulin triggers the resumption of meiosis in amphibian oocytes

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 c...

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Detalles Bibliográficos
Formato: Texto
Lenguaje:English
Publicado: The Rockefeller University Press 1981
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2111798/
https://www.ncbi.nlm.nih.gov/pubmed/6265465
Descripción
Sumario: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.