Effect of Multiple Phosphorylations on Movement of Smooth Muscle and Cytoplasmic Myosin
Smooth muscle contraction is initiated by phosphorylation of the 20,000 Da light chain subunit of myosin (Sellers and Adelstein, 1987; Hartshorne, 1987). The enzyme responsible for this phosphorylation, myosin light chain (MLC) kinase, is dependent upon both calcium and calmodulin for activity. In addition to its role in muscle contraction, myosin plays an important contractile role in many nonmuscle cells (Korn and Hammer, 1988). This cytoplasmic myosin is also regulated by light chain phosphorylation. Phosphorylation of smooth muscle and cytoplasmic myosin by MLC kinase results in their activation as judged by a large increase in the actin-activated MgATPase activity.
KeywordsSucrose Leukemia MgCl2 Turkey EGTA
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- Bengur, A. R., Harvey, E. V., and Sellers, J. R., 1987a, Phosphorylation of platelet myosin by protein kinase C: in vitro and in vivo studies, J. Cell Biol. 105, 656a.Google Scholar
- Colburn, J. C, Michnoff, C. H. Shu, L-C, Slaughter, C. A., Kamm, K. E., and Stull, J. T., 1988, Sites phosphorylated in myosin ligh chain in contracting smooth muscle, J. Biol. Chem., in press.Google Scholar
- Erodi, F., Barany, M., and Barany, K., 1987, Myosin light chain isoforms and their phosphorylation in arterial smooth muscle, Cir. Res. 61, 898.Google Scholar
- Hartshorne, D. J., 1987, Biochemistry of the contractile process in smooth muscle, in: “Physiology of the Gastrointestinal Tract”, 2nd ed., L. R. Johnson, ed., Raven Press, New York.Google Scholar
- Ludowyke, R. I., Peleg, I., Beaven, M. A., and Adelstein, R. S., 1987, Analysis of phosphorylation of myosin heavy and light chains during antigen stimulation of basophil leukemic cells, J. Cell Biol. 105, 118a.Google Scholar
- Umemoto, S., Bengur, A. R., and Sellers, J. R., 1989, Effect of multiple phosphorylations of smooth muscle and cytoplasmic myosins on movement in an in vitro motility assay, J. Biol. Chem., in press.Google Scholar