title: Downregulation of the translation elongation factor 2 kinase in Xenopus laevis oocytes at the final stages of oogenesis.
abstract: Phosphorylation of translation elongation factor 2(eEF-2) by a specific Ca2+/calmodulin-dependent eEF-2 kinase plays an important role in the regulation of protein synthesis in mammalian cells. We show here that an eEF-2 kinase similar to the mammalian enzyme is present in tissues of the amphibian Xenopus laevis. We investigated changes in the activity of eEF-2 kinase in extracts of Xenopus oocytes at different stages of oogenesis. The eEF-2 kinase activity was constant from stage I to stage IV of oogenesis, but dramatically decreased after stage IV. Extracts of fully grown stage-VI oocytes showed no eEF-2 kinase activity. However, when extracts were analyzed by two-dimensional gel electrophoresis, eEF-2 was found to be present mostly, if not exclusively, in the dephosphorylated form throughout oogenesis. It is suggested that eEF-2 kinase disappears late in oogenesis to make protein synthesis insensitive to changes in intracellular Ca2+ concentration. This may be important for the induction of meiotic maturation.
authors.affiliation: Institute of Protein Research, Academy of Sciences, Moscow Region, USSR.
authors.forename: K V
authors.initials: KV
authors.lastname: Severinov
authors.forename: E G
authors.initials: EG
authors.lastname: Melnikova
authors.forename: A G
authors.initials: AG
authors.lastname: Ryazanov
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002147:Calmodulin / Q000502:physiology; D054736:Elongation Factor 2 Kinase; D004790:Enzyme Induction; D005260:Female; D009865:Oocytes / Q000378:metabolism*; D009866:Oogenesis; D010441:Peptide Chain Elongation, Translational; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors / Q000378:metabolism*; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D015398:Signal Transduction; D014982:Xenopus laevis
chemical_list: D002147:Calmodulin; D020652:Peptide Elongation Factor 2; D010445:Peptide Elongation Factors; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D054736:Elongation Factor 2 Kinase; D002118:Calcium