Identification of MAPKAPK homolog (MAPKAPK-4) as a myosin II regulatory light-chain kinase in sea urchin egg extracts.
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.
Komatsu
S
S
Department of Biological Science, Faculty of Science, Hiroshima University, Higashi-Hiroshima, Japan.
Murai
N
N
Totsukawa
G
G
Abe
M
M
Akasaka
K
K
Shimada
H
H
Hosoya
H
H
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000235:genetics* / Q000378:metabolism; D002645:Chickens; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004789:Enzyme Activation; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D008969:Molecular Sequence Data; D010063:Ovum / Q000201:enzymology*; D010766:Phosphorylation; D011817:Rabbits; D012617:Sea Urchins; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D017871:Calcium-Calmodulin-Dependent Protein Kinases