Filament assembly and regulation of the actin-activated ATPase activity of thymus myosin

The effects of light chain phosphorylation on the actin-activated ATPase activity and filament assembly of calf thymus cytoplasmic myosin were examined under a variety of conditions. When unphosphorylated and phosphorylated thymus myosins were monomeric, their MgATPase activities were not activated...

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Bibliographic Details
Published in:Biochemistry (Easton) 1988-08, Vol.27 (17), p.6236-6242
Main Authors: Wagner, Paul D, Vu Ngoc Diep
Format: Article
Language:English
Subjects:
Actins - metabolism
adenosinetriphosphatase
Analytical, structural and metabolic biochemistry
Animals
Biological and medical sciences
Ca(2+) Mg(2+)-ATPase - metabolism
Cattle
Contractile proteins
Cytoskeleton - metabolism
Enzyme Activation
Fundamental and applied biological sciences. Psychology
Holoproteins
Kinetics
Macromolecular Substances
myosin
Myosins - metabolism
Phosphorylation
Proteins
Thymus Gland - enzymology
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Summary:The effects of light chain phosphorylation on the actin-activated ATPase activity and filament assembly of calf thymus cytoplasmic myosin were examined under a variety of conditions. When unphosphorylated and phosphorylated thymus myosins were monomeric, their MgATPase activities were not activated or only very slightly activated by actin, but when they were filamentous, their MgATPase activities were stimulated by actin. The phosphorylated myosin remained filamentous at lower Mg2+ concentrations and higher KC1 concentrations than did the unphosphorylated myosin, and the myosin concentration required for filament assembly was lower for phosphorylated myosin than for unphosphorylated myosin. By varying the myosin concentration, it was possible to have under the same assay conditions mostly monomeric myosin or mostly filamentous myosin; under these conditions, the actin-activated ATPase activities of the filamentous myosins were much greater than those of the monomeric myosins. The addition of phosphorylated myosin to unphosphorylated myosin promoted the assembly of unphosphorylated myosin into filaments. These results suggest that phosphorylation may regulate the actomyosin-based motile activities in vertebrate nonmuscle cells by regulating myosin filament assembly.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00417a007