Resolution of distinct rotational substeps by submillisecond kinetic analysis of F1-ATPase
Resolution of distinct rotational substeps by submillisecond kinetic analysis of F1-ATPase
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DOI：
10.1038/35073513
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发表时间：
2001-04-19
期刊：
影响因子：
64.8
通讯作者：
Itoh, H
中科院分区：
文献类型：
--
作者：
Yasuda, R;Noji, H;Itoh, H
酶F-1-ATP酶已被证明是一个旋转马达，其中中心γ亚基在由α（3）β（3）亚基组成的圆柱体内旋转。在低ATP浓度下，马达以离散的120度步长旋转，这与三个β亚基上的连续ATP水解一致。步进的机制尚不清楚。在这里，我们通过高速成像显示，120度的步骤由大约90度和30度的子步骤组成，每个子步骤只需要几分之一毫秒。ATP结合驱动90度子步骤，并且30度子步骤可能由水解产物的释放驱动。这两个子步骤由两个约1 ms的反应分开，它们一起占据了ATP水解循环的大部分。该方案可能适用于全速旋转（类似于饱和ATP时每秒130转），直到偶尔在纳摩尔ATP浓度下步进，并支持F-1-ATP酶反向旋转ATP合成的结合变化模型。
The enzyme F-1-ATPase has been shown to be a rotary motor in which the central gamma -subunit rotates inside the cylinder made of alpha (3)beta (3) subunits. At low ATP concentrations, the motor rotates in discrete 120 degrees steps, consistent with sequential ATP hydrolysis on the three beta -subunits. The mechanism of stepping is unknown. Here we show by high-speed imaging that the 120 degrees step consists of roughly 90 degrees and 30 degrees substeps, each taking only a fraction of a millisecond. ATP binding drives the 90 degrees substep, and the 30 degrees substep is probably driven by release of a hydrolysis product. The two substeps are separated by two reactions of about 1 ms, which together occupy most of the ATP hydrolysis cycle. This scheme probably applies to rotation at full speed (similar to 130 revolutions per second at saturating ATP) down to occasional stepping at nanomolar ATP concentrations, and supports the binding-change model for ATP synthesis by reverse rotation of F-1-ATPase.