The F1 motor is a rotating molecular motor that ensures a tight chemomechanical coupling between ATP hydrolysis/synthesis reactions and rotation steps. However, the mechanism underlying this tight coupling remains to be elucidated. In this study, we used electrorotation in single-molecule experiments using an F1βE190D mutant to demonstrate that the stall torque was significantly smaller than the wild-type F1, indicating a loose coupling of this mutant, despite showing similar stepping torque as the wild-type. Experiments on the ATPase activity after heat treatment and gel filtration of the α3β3-subcomplex revealed the unstable structure of the βE190D mutant. Our results suggest that the tight chemomechanical coupling of the F1 motor relies on the structural stability of F1. We also discuss the difference between the stepping torque and the stall torque.

中文翻译：

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F1 电机的紧密化学机械耦合依赖于结构稳定性。

F1 电机是一种旋转分子电机，可确保 ATP 水解/合成反应和旋转步骤之间的化学机械紧密耦合。然而，这种紧密耦合的机制仍有待阐明。在这项研究中，我们在使用 F1βE190D 突变体的单分子实验中使用电旋转来证明失速扭矩明显小于野生型 F1，表明该突变体的松散耦合，尽管表现出与野生型相似的步进扭矩. α3β3-亚复合物热处理和凝胶过滤后 ATP 酶活性的实验揭示了 βE190D 突变体的不稳定结构。我们的结果表明 F1 电机的紧密化学机械耦合依赖于 F1 的结构稳定性。