Role of Actin in the Myosin-Linked Ca2+-Regulation of ATP-Dependent Interaction between Actin and Myosin of a Lower Eukaryote, Physarum polycephalum1
書誌事項
- 公開日
- 1991-10
- DOI
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- 10.1093/oxfordjournals.jbchem.a123611
- 公開者
- Oxford University Press (OUP)
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説明
Actin-activated ATPase activity of myosin from Physarum polycephalum decreases when it binds Ca2+ and increases when it loses Ca2+. This Ca-inhibition is observed with phosphorylated myosin [Kohama, K. (1990) Trend, Pharmacol. Sci. 11, 433-435]. The activity of dephosphorylated myosin remained at a low level both in the presence and absence of Ca2+, although Ca(2+)-binding ability was much the same as that of the phosphorylated myosin. The effect of phosphorylation has been studied at a conventional actin concentration, which is comparable with that of myosin by weight. When the concentration of actin was increased by 10 times, the dephosphorylated myosin became actin-activatable in the absence of Ca2+, and Ca-inhibition was recovered. As actin exists quite abundantly in non-muscle cells of Physarum, myosin phosphorylation plays virtually no role in regulating actin-myosin-ATP interaction in vivo. Physiologically the interaction may be regulated by Ca2+ by binding to and subsequent release from myosin. Latex beads coated by either phosphorylated or dephosphorylated myosin moved ATP-dependently on the actin cables of Characeae cells to the same extent in the absence of Ca2+, but the movement was abolished by increasing Ca2+. When the interaction was examined by monitoring the movement of actin filaments on myosin fixed on a coverslip, the movement and Ca-inhibition of the movement were detected with phosphorylated, not dephosphorylated, myosin [Okagaki, T., Higashi-Fujime, S.,Kohama, K. (1989) J. Biochem. 106, 955-957].(ABSTRACT TRUNCATED AT 250 WORDS)
収録刊行物
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- The Journal of Biochemistry
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The Journal of Biochemistry 110 (4), 508-513, 1991-10
Oxford University Press (OUP)
