Regulation of myosin self-assembly: phosphorylation of Dictyostelium heavy chain inhibits formation of thick filaments.
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<jats:p>Dictyostelium myosin is composed of two heavy chains and two pairs of light chains in a 1:1:1 stoichiometry. Myosin purified from amoebae grown in medium containing [32P]phosphate had two of the subunits labeled (0.2-0.3 mol of phosphate per mol of 210,000-dalton heavy chains and approximately 0.1 mol of phosphate per mol of 18,000-dalton light chain). Kinase activities specific for the 210,000-dalton and for the 18,000-dalton subunits have been identified in extracts of Dictyostelium amoebae, and the heavy chain kinase has been purified 50-fold. This kinase phosphorylated Dictyostelium myosin to a maximum of 0.5-1.0 mol of phosphate per mol of heavy chain. Heavy chain phosphate, but not light chain phosphate, can be removed with bacterial alkaline phosphatase. Actin-activated myosin ATPase increased 80% when phosphorylated myosin was dephosphorylated to a level of approximately 0.06 mol of phosphate per mol of heavy chain. This effect could be reversed by rephosphorylating the myosin. The ability of myosin to self-assemble into thick filaments was inhibited by heavy chain phosphorylation. For example, in 80-100 mM KCl, only 10-20% of the myosin was assembled into thick filaments when the heavy chains were fully phosphorylated. Removal of the heavy chain phosphate resulted in 70-90% thick filament formation. This effect on self-assembly could be reversed by rephosphorylating the dephosphorylated myosin. These findings suggest that heavy chain phosphorylation may regulate cell contractile events by altering the state of myosin assembly.</jats:p>
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- Proceedings of the National Academy of Sciences
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Proceedings of the National Academy of Sciences 77 (12), 7292-7296, 1980-12
Proceedings of the National Academy of Sciences
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詳細情報 詳細情報について
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- CRID
- 1360292620251358720
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- NII論文ID
- 30016269674
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- ISSN
- 10916490
- 00278424
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- データソース種別
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