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  • Title: Regulatory mechanism in arterial smooth muscle contraction.
    Author: Koizumi T, Ito Y, Ebashi S.
    Journal: Recent Adv Stud Cardiac Struct Metab; ; 11():185-91. PubMed ID: 145628.
    Abstract:
    The regulatory mechanism in the aortic actomyosin system was studied. Superprecipitation of desensitized aortic myosin B was not exhibited even in the presence of Ca2+, but was observable only in the presence of native tropomyosin and Ca2+. Reconstituted actomyosin composed of pure aortic myosin and pure skeletal actin did not show superprecipitation. Addition of aortic native tropomyosin and Ca2+ caused a marked superprecipitation. The ATPase of reconstituted actomyosin was enhanced three- or fourfold by aortic native tropomyosin and Ca2+. The extent of superprecipitation of aortic myosin B did not show a biphasic type of response to Mg-ATP concentration. Thus, aortic native tropomyosin induces a real activation of the myosin, actin, and ATP system in the presence of Ca2+, in contrast with the case of skeletal native tropomyosin, which induces the depression of skeletal myosin-actin-ATP interaction in the absence of Ca2+.
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