Abstract
The dependenee of the onset and course of turbidity changes (superprecipitation) induced by ATP were studied in a naturai actomyosin suspension with the dephosphorylated and phosphorylated forms of light chains (LC 2) of myosin. It was found that the onset and time course of the changes in turbidity of the natural actomyosin suspension are strongly dependent on the (phosphorylated and dephosphorylated) form of these chains of myosin. The ATPase activity of actomyosin with phosphorylated LC 2 was lower and the half-time for achieving maximal turbidity of actomyosin suspension after addition of ATP was higher than that of actomyosin with dephosphorylated LC 2. Natural actomyosin preparations contain endogenous light-chain kinase and phosphatase. The changes of turbidity induced by ATP in the natural actomyosin suspension are greatly diminished in the presence of phosphate. Thiophosphorylation of LC 2 of myosin leads to a decrease of the extent of superprecipitation of natural actomyosin. The release of [ 32 P]phosphate from actomyosin containing [ 32P]ATP-phosphorylated LC 2 of myosin increases with increased turbidity of the actomyosin suspension. The change of the form of LC 2 as a kind of additional myosin-linked regulation of superprecipiration is discussed.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology
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