Inhibition of Mg ++ ATPase activity of actin-activated Acanthamoeba myosin by muscle troponin-tropomyosin: implications for the mechanism of control of amoeba motility and muscle contraction |
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Authors: | T D Pollard E Eisenberg E D Korn W W Kielley |
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Institution: | Laboratory of Biochemistry National Heart and Lung Institute National Institutes of Health, Bethesda, Maryland 20014 USA |
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Abstract: | Troponin-tropomyosin is known to inhibit the Mg++ATPase activity of muscle actomyosin in the absence, but not in the presence, of Ca++. In contrast, we have now found that muscle troponin-tropomyosin inhibits the Mg++ATPase activity of muscle actin-activated myosin both in the presence and the absence of Ca++. Addition of purified tropomyosin and troponins-I, C and T demonstrated that it is troponin-T that acts differently in the two systems which differ only in the source of the myosin. These data suggest that myosin, as well as actin, plays a role in the troponin-tropomyosin control of muscle contraction and make it unlikely that control proteins identical to troponin-tropomyosin function in this amoeba. |
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