PMID: 4294198Nov 1, 1967Paper

The contractile and control sites of natural actomyosin

The Journal of General Physiology
H M LEVY, E M RYAN

Abstract

The various contractile and control sites of natural actomyosin gel were studied by comparing the kinetics of ATP hydrolysis with those of gel contraction, measured as an increase in turbidity. Contraction of actomyosin gel seems to require the cooperative reaction of ATP (with Mg) at two different sites. One of these sites catalyzes the hydrolysis of ATP and most probably contributes the driving force for contraction; the binding of ATP to the other site appears to break certain links that retard movement of the gel components. At limiting concentrations of ATP, the rate of contraction seems to depend on the rate of breaking these links as well as on the rate of ATP hydrolysis. But when both sites are saturated, the rate of contraction appears to be limited only by the rate of ATP hydrolysis. In addition to these two contractile sites, there are also two different control sites. At one, the relaxing site, the binding of ATP with Mg inhibits ATP hydrolysis and gel contraction. At the other, the binding of calcium activates contraction by overcoming the inhibitory action of Mg and ATP at the relaxing site. This control system-inhibition by substrate and disinhibition by calcium-can be selectively inactivated by heat and reactiva...Continue Reading

References

Jan 1, 1966·Annual Review of Biochemistry·J Gergely
Sep 1, 1960·Archives of Biochemistry and Biophysics·Y TONOMURA, J YOSHIMURA
Apr 1, 1964·Biochemistry·W W CLELAND
Aug 1, 1962·Archives of Biochemistry and Biophysics·K LAKID R KOMINZ

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Citations

Aug 1, 1968·Comparative Biochemistry and Physiology·G W De Villafranca
May 1, 1969·Comparative Biochemistry and Physiology·G W De Villafranca, L K Campbell
Jun 15, 1975·Comparative Biochemistry and Physiology. B, Comparative Biochemistry·F FuchsE M Barns
Mar 1, 1972·The Journal of General Physiology·P W BrandtH Grundfest
Oct 5, 1973·Circulation Research·P I Polimeni, E Page
Jul 26, 1972·Nature: New Biology·R D Bremel, A Weber
Nov 3, 1970·Biochimica Et Biophysica Acta·D J Hartshorne, J L Daniel

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