Arch Biochem Biophys 1997 Jul 01;3431:55-62. doi: 10.1006/abbi.1997.9966.

Identification of MAPKAPK homolog (MAPKAPK-4) as a myosin II regulatory light-chain kinase in sea urchin egg extracts.

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We identified and cloned a homolog of mammalian mitogen-activated protein kinase-activated protein kinase (MAPKAPK)-2 and -3 from sea urchin, Hemicentrotus pulcherrimus. The obtained cDNA clone was composed of 350 amino acid residues which contain MAPK phosphorylation sites and the bipartite nuclear localization signal sites in its C-terminal domain. The clone showed 65.4 and 66.7% amino acid residue identity to human MAPKAPK-2 and -3, respectively. Phylogenetic analysis revealed that the homolog can be classified into a distinct group of MAPKAPK and, therefore, the identified homolog was designated as MAPKAPK-4. Biochemical characterization was performed using recombinant glutathione S-transferase (GST)-MAPKAPK-4 fusion protein. The protein kinase activity of GST-MAPKAPK-4 was activated by MAPK and this enabled the kinase to phosphorylate both glycogen synthase N-terminal peptide and the regulatory light chain of myosin II in vitro. Northern blot analysis showed that MAPKAPK-4 was expressed throughout the development of sea urchin embryos. These observations suggest that MAPKAPK-4 may play an important role in the regulation of myosin II activity during the development of sea urchin.

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Genes referenced: cep152 LOC100887844 LOC576114 LOC578305 LOC586799 LOC594349 LOC752853