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XB-ART-24886
Mol Cell Biol May 1, 1991; 11 (5): 2517-28.
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Tyrosine phosphorylation and activation of homologous protein kinases during oocyte maturation and mitogenic activation of fibroblasts.

Posada J , Sanghera J , Pelech S , Aebersold R , Cooper JA .


Abstract
Meiotic maturation of Xenopus and sea star oocytes involves the activation of a number of protein-serine/threonine kinase activities, including a myelin basic protein (MBP) kinase. A 44-kDa MBP kinase (p44mpk) purified from mature sea star oocytes is shown here to be phosphorylated at tyrosine. Antiserum to purified sea star p44mpk was used to identify antigenically related proteins in Xenopus oocytes. Two tyrosine-phosphorylated 42-kDa proteins (p42) were detected with this antiserum in Xenopus eggs. Xenopus p42 chromatographs with MBP kinase activity on a Mono Q ion-exchange column. Tyrosine phosphorylation of Xenopus p42 approximately parallels MBP kinase activity during meiotic maturation. These results suggest that related MBP kinases are activated during meiotic maturation of Xenopus and sea star oocytes. Previous studies have suggested that Xenopus p42 is related to the mitogen-activated protein (MAP) kinases of culture mammalian cells. We have cloned a MAP kinase relative from a Xenopus ovary cDNA library and demonstrate that this clone encodes the Xenopus p42 that is tyrosine phosphorylated during oocyte maturation. Comparison of the sequences of Xenopus p42 and a rat MAP kinase (ERK1) and peptide sequences from sea star p44mpk indicates that these proteins are close relatives. The family members appear to be tyrosine phosphorylated, and activated, in different contexts, with the murine MAP kinase active during the transition from quiescence to the G1 stage of the mitotic cell cycle and the sea star and Xenopus kinases being active during M phase of the meiotic cell cycle.

PubMed ID: 1708093
PMC ID: PMC360021
Article link: Mol Cell Biol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: cdk20 mapk1 mbp

References [+] :
Aebersold, Internal amino acid sequence analysis of proteins separated by one- or two-dimensional gel electrophoresis after in situ protease digestion on nitrocellulose. 1987, Pubmed