Identification of a phosphorylation site on skeletal muscle myosin light chain kinase that becomes phosphorylated during muscle contraction.
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.
Haydon
Claire E
CE
MRC Protein Phosphorylation Unit, University of Dundee, Dundee, DD1 5EH, Scotland, UK.
Watt
Peter W
PW
Morrice
Nick
N
Knebel
Axel
A
Gaestel
Matthias
M
Cohen
Philip
P
D048948:14-3-3 Proteins; D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D004558:Electric Stimulation; D006614:Hindlimb / Q000502:physiology; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000201:enzymology*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011817:Rabbits; D012694:Serine / Q000378:metabolism; D013379:Substrate Specificity; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2
D048948:14-3-3 Proteins; D000199:Actins; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D020928:Mitogen-Activated Protein Kinases; D009219:Myosin-Light-Chain Kinase; D017346:Protein Serine-Threonine Kinases; D012694:Serine; D014446:Tyrosine 3-Monooxygenase; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2