Catalytic fragment of protein kinase C exhibits altered substrate specificity toward smooth muscle myosin light chain.
Smooth muscle myosin light chain (LC) can be phosphorylated by myosin light chain kinase (MLCK) at Ser19 and Thr18 and by protein kinase C (PKC) at Thr9 and Ser1 or Ser2 under the in vitro assay conditions. Conversion of PKC to the spontaneously active protein kinase M (PKM) by proteolysis resulted in a change in the substrate specificity of the kinase. PKM phosphorylated both sets of sites in LC recognized by MLCK and PKC as analyzed by peptide mapping analysis. The PKM-catalyzed phosphorylation of these sites was not greatly affected by a MLCK inhibitor, ML-9, nor by the activators of MLCK, Ca2+ and calmodulin.
Nakabayashi
H
H
Endocrinology and Reproduction Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892.
Sellers
J R
JR
Huang
K P
KP
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D015180:Electrophoresis, Gel, Two-Dimensional; D005895:Gizzard, Avian / Q000378:metabolism; D007525:Isoelectric Focusing; D007700:Kinetics; D008969:Molecular Sequence Data; D009130:Muscle, Smooth / Q000378:metabolism*; D009219:Myosin-Light-Chain Kinase / Q000378:metabolism; D009218:Myosins / Q000378:metabolism*; D010446:Peptide Fragments / Q000302:isolation & purification / Q000378:metabolism; D010449:Peptide Mapping; D011493:Protein Kinase C / Q000378:metabolism*; D013379:Substrate Specificity; D014357:Trypsin; D014422:Turkeys
D010446:Peptide Fragments; D011493:Protein Kinase C; D009219:Myosin-Light-Chain Kinase; D014357:Trypsin; D009218:Myosins