Cooperative turning on of myosin subfragment 1 adenosinetriphosphatase activity by the troponin-tropomyosin-actin complex.
Cooperative turning on of myosin subfragment 1 adenosinetriphosphatase activity by the troponin-tropomyosin-actin complex.
复制标题
肌钙蛋白-原肌球蛋白-肌动蛋白复合物协同开启肌球蛋白亚片段 1 腺苷三磷酸酶活性。
作者：
David L. Williams;L. Greene;E. Eisenberg
在肌肉调节领域，关于单独的Ca 2+是否能够将肌肉从放松状态转变为完全活跃状态，或者跨桥结合是否也有助于打开肌肉收缩，仍然存在争议。我们以前的研究结合肌球蛋白亚片段1（S-1）的肌钙蛋白-原肌球蛋白-肌动蛋白复合物（调节肌动蛋白）在缺乏ATP的情况下表明，即使在Ca 2+，严格的交叉桥的结合是必要的完全打开调节肌动蛋白。在本研究中，我们证明了这也是acto.S-1 ATP酶活性开启的情况。Ca 2+本身不能完全开启acto.S-1 ATP酶活性;在低肌动蛋白浓度下，当在Ca 2+存在下通过刚性交叉桥的结合完全开启受调节的肌动蛋白时，ATP酶活性几乎增加10倍。ATP酶活性的这种大幅度增加并不发生，因为S-1.ATP与肌动蛋白的结合增加了; S-1.ATP与最大关闭和最大打开调节的肌动蛋白的结合几乎相同。ATP酶活性的增加是由于Pi释放速率的显著增加，因此当被调节的肌动蛋白被完全打开时，Pi释放变得如此迅速，以至于限速步骤先于Pi释放步骤。这些结果表明，虽然Ca 2+，单独，不完全打开调节肌动蛋白丝在溶液中，刚性交叉桥的绑定可以打开它完全。如果产生力的横桥在体内起着与体外僵硬横桥相同的作用，则可能存在Ca 2+和横桥结合在开启肌肉收缩中的协同作用，这可以极大地提高肌纤维对Ca 2+的反应。
In the field of muscle regulation, there is still controversy as to whether Ca2+, alone, is able to shift muscle from the relaxed to the fully active state or whether cross-bridge binding also contributes to turning on muscle contraction. Our previous studies on the binding of myosin subfragment 1 (S-1) to the troponin-tropomyosin-actin complex (regulated actin) in the absence of ATP suggested that, even in Ca2+, the binding of rigor cross-bridges is necessary to turn on regulated actin fully. In the present study, we demonstrate that this is also the case for the turning on of the acto.S-1 ATPase activity. By itself, Ca2+ does not fully turn on the acto.S-1 ATPase activity; at low actin concentration, there is almost a 10-fold increase in ATPase activity when the regulated actin is fully turned on by the binding of rigor cross-bridges in the presence of Ca2+. This large increase in ATPase activity does not occur because the binding of S-1.ATP to actin is increased; the binding of S-1.ATP is almost the same to maximally turned-off and maximally turned-on regulated actin. The increase in ATPase activity occurs because of a marked increase in the rate of Pi release so that when the regulated actin is fully turned on, Pi release becomes so rapid that the rate-limiting step precedes the Pi release step. These results suggest that, while Ca2+, alone, does not fully turn on the regulated actin filament in solution, the binding of rigor cross-bridges can turn it on fully. If force-producing cross-bridges play the same role in vivo as rigor cross-bridges in vitro, there may be a synergistic effect of Ca2+ and cross-bridge binding in turning on muscle contraction which could greatly sharpen the response of the muscle fiber to Ca2+.
登录
查看更多内容
DOI：
--
发表时间：
1981
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Chalovich,JM;Chock,PB;Eisenberg,E
通讯作者：
Eisenberg,E
原肌球蛋白和肌钙蛋白-原肌球蛋白对肌动球蛋白亚片段 1 ATP 酶的双重作用。
DOI：
--
发表时间：
1982
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Lehrer,SS;Morris,EP
通讯作者：
Morris,EP
骨骼肌和平滑肌肌动亚片段 1 的 ATP 酶机制。
DOI：
--
发表时间：
1984
期刊：
The Journal of biological chemistry
影响因子：
--
作者：
Rosenfeld,SS;Taylor,EW
通讯作者：
Taylor,EW
肌球蛋白亚片段 1 与松弛的肌动蛋白丝和松弛的空间模型结合。
影响因子：
2.9
作者：
Murray,JM;Weber,A;Knox,MK
通讯作者：
Knox,MK
DOI：
10.1073/pnas.77.8.4717
发表时间：
1980-01-01
期刊：
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA-BIOLOGICAL SCIENCES
影响因子：
--
作者：
BRANDT, PW;COX, RN;KAWAI, M
通讯作者：
KAWAI, M