二价阳离子对肌动球蛋白三磷酸腺苷酶的影响及其受原肌球蛋白和肌钙蛋白的修饰作用。

Effect of bivalent cations on the adenosine triphosphatase of actomyosin and its modification by tropomyosin and troponin.

作者信息

Schaub M C, Ermini M

出版信息

Biochem J. 1969 Mar;111(5):777-83. doi: 10.1042/bj1110777.

DOI:10.1042/bj1110777

PMID:4239323

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1187607/

Abstract

After removal of tropomyosin and troponin from the ;natural' actomyosin complex, the adenosine triphosphatase activity of the resulting ;desensitized' actomyosin is stimulated to the same extent by various bivalent cations with an ionic radius in the range 0.65-0.99å when tested at optimum concentration of the metal ion in the presence of 2.5mm-ATP at low ionic strength and pH7.6. Under identical conditions the adenosine triphosphatase activity of myosin alone is stimulated to an appreciable extent only by Ca(2+) (ionic radius 0.99å). 2. Tropomyosin narrows the range of size of the stimulatory cations by inhibiting specifically the adenosine triphosphatase activity of ;desensitized' actomyosin when stimulated by Ca(2+) or the slightly smaller Cd(2+) (ionic radius 0.97å). Tropomyosin has no effect on the adenosine triphosphatase activity of ;desensitized' actomyosin when stimulated by the smaller cations, nor on the Ca(2+)-activated adenosine triphosphatase activity of myosin alone. 3. The adenosine triphosphatase activity of the ;natural' actomyosin system (containing tropomyosin and troponin) stimulated by the smallest cation, Mg(2+) (ionic radius 0.65å), is low when the system is deprived of Ca(2+) but high in the presence of small amounts of Ca(2+). This sensitivity to Ca(2+) seems to be a unique feature of the Mg(2+)-stimulated system. 4. The changes in specificity of the myosin adenosine triphosphatase activity in its requirement for bivalent cations caused by interaction with actin, tropomyosin and troponin primarily concern the size of the metal ions. The effects on enzymic properties of myofibrils due to tropomyosin and troponin can be demonstrated at low and at physiological ionic strength.

摘要

从“天然”肌动球蛋白复合物中去除原肌球蛋白和肌钙蛋白后，在低离子强度和pH7.6条件下，于2.5mM - ATP存在时，在金属离子的最佳浓度下进行测试，所得“脱敏”肌动球蛋白的腺苷三磷酸酶活性受到离子半径在0.65 - 0.99埃范围内的各种二价阳离子同等程度的刺激。在相同条件下，单独的肌球蛋白的腺苷三磷酸酶活性仅受到Ca(2+)（离子半径0.99埃）的显著刺激。2. 原肌球蛋白通过特异性抑制“脱敏”肌动球蛋白在受Ca(2+)或稍小的Cd(2+)（离子半径0.97埃）刺激时的腺苷三磷酸酶活性，缩小了刺激阳离子的大小范围。当受较小阳离子刺激时，原肌球蛋白对“脱敏”肌动球蛋白的腺苷三磷酸酶活性没有影响，对单独的肌球蛋白的Ca(2+)激活的腺苷三磷酸酶活性也没有影响。3. 由最小的阳离子Mg(2+)（离子半径0.65埃）刺激的“天然”肌动球蛋白系统（含有原肌球蛋白和肌钙蛋白）的腺苷三磷酸酶活性，在系统缺乏Ca(2+)时较低，但在存在少量Ca(2+)时较高。这种对Ca(2+)的敏感性似乎是Mg(2+)刺激系统的独特特征。4. 肌球蛋白腺苷三磷酸酶活性在与肌动蛋白、原肌球蛋白和肌钙蛋白相互作用时对二价阳离子需求的特异性变化主要涉及金属离子的大小。原肌球蛋白和肌钙蛋白对肌原纤维酶学性质的影响可在低离子强度和生理离子强度下得到证实。