期刊
ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS
卷 397, 期 2, 页码 224-231出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1006/abbi.2001.2625
关键词
MAPKAP kinase-2; myosin light chain kinase; muscle contraction; mouse knockout; calmodulin; calcium ions; 14-3-3 proteins; calmodulin-dependent protein kinase-2; protein kinase specificity
A protein phosphorylated efficiently in vitro by MAP kinase-activated protein kinase-2 (MAPKAP-K2) was purified from skeletal muscle extracts and identified as the calcium/calmodulin-dependent myosin light chain kinase (MLCK). The phosphorylation site was mapped to Ser(161), a residue shown previously to be autophosphorylated by MLCK. The residue equivalent to Ser(161) became phosphorylated in vivo when rat hindlimbs were stimulated electrically. However, phosphorylation was triggered within seconds, whereas activation of MAPKAP-K2 required several minutes. Moreover, contraction-induced Ser(161) phosphorylation was similar in wild-type or MAPKAP-K2-/- mice. These results indicate that contraction-induced phosphorylation is probably catalyzed by MLCK and not MAPKAP-K2. Ser(161) phosphorylation induced the binding of MLCK to 14-3-3 proteins, but did not detectably affect the kinetic properties of MLCK. The sequence surrounding Ser(161) is unusual in that residue 158 is histidine. Previously, an arginine located three residues N-terminal to the site of phosphorylation was thought to be critical for the specificity of MAPKAP-K2. (C) 2001 Elsevier Science.
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