Kyoto University Graduate School of Biostudies, Kyoto, Japan.
FEBS J. 2011 Sep;278(17):3025-31. doi: 10.1111/j.1742-4658.2011.08222.x. Epub 2011 Jul 18.
Studies of ion pumps, such as ATP synthetase and Ca(2+)-ATPase, have a long history. The crystal structures of several kinds of ion pump have been resolved, and provide static pictures of mechanisms of ion transport. In this study, using fast-scanning atomic force microscopy, we have visualized conformational changes in the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA) in real time at the single-molecule level. The analyses of individual SERCA molecules in the presence of both ATP and free Ca(2+) revealed up-down structural changes corresponding to the Albers-Post scheme. This fluctuation was strongly affected by the ATP and Ca(2+) concentrations, and was prevented by an inhibitor, thapsigargin. Interestingly, at a physiological ATP concentrations, the up-down motion disappeared completely. These results indicate that SERCA does not transit through the shortest structure, and has a catalytic pathway different from the ordinary Albers-Post scheme under physiological conditions.
离子泵（如 ATP 合酶和 Ca(2+)-ATP 酶）的研究已有很长的历史。几种离子泵的晶体结构已被解析，为离子运输的机制提供了静态图片。在这项研究中，我们使用快速扫描原子力显微镜，在单分子水平上实时可视化肌浆网 Ca(2+)-ATP 酶（SERCA）的构象变化。在存在 ATP 和游离 Ca(2+)的情况下，对单个 SERCA 分子的分析表明，与 Albers-Post 方案相对应的上下结构变化。这种波动强烈受到 ATP 和 Ca(2+)浓度的影响，并被抑制剂 thapsigargin 所阻止。有趣的是，在生理 ATP 浓度下，上下运动完全消失。这些结果表明，SERCA 不会通过最短的结构，并且在生理条件下具有不同于普通 Albers-Post 方案的催化途径。
