The ring-like ATPase complexes in the AAA+ family perform diverse cellular functions that require coordination between the conformational transitions of their individual ATPase subunits^1,2. How the energy from ATP hydrolysis is captured to perform mechanical work by these coordinated movements is not known. In this study, we developed a novel approach for delineating the nucleotide-dependent free-energy landscape (FEL) of the proteasome’s heterohexameric ATPase complex based on complementary structural and kinetic measurements. We used the FEL to simulate the dynamics of the proteasome and quantitatively evaluated the predicted structural and kinetic properties. The FEL model predictions were widely consistent with experimental observations in this and previous studies and suggested novel features of the mechanism of proteasomal ATPase. We find that the cooperative movements of the ATPase subunits result from the design of the ATPase hexamer entailing a unique free-energy minimum for each nucleotide-binding state. ATP hydrolysis dictates the direction of substrate translocation by triggering an energy-dissipating conformational transition of the ATPase complex.

中文翻译：

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经验能量景观揭示蛋白酶体在多肽易位中的机制

AAA+ 家族中的环状 ATPase 复合物执行多种细胞功能，这些功能需要在其各个 ATPase 亚基的构象转换之间进行协调^1,2. 尚不清楚 ATP 水解产生的能量如何通过这些协调运动被捕获以执行机械功。在这项研究中，我们开发了一种新的方法，用于基于互补的结构和动力学测量来描绘蛋白酶体的异六聚体 ATP 酶复合物的核苷酸依赖性自由能景观 (FEL)。我们使用 FEL 来模拟蛋白酶体的动力学并定量评估预测的结构和动力学特性。FEL 模型预测与本研究和先前研究中的实验观察结果广泛一致，并提出了蛋白酶体 ATP 酶机制的新特征。我们发现 ATPase 亚基的协同运动源于 ATPase 六聚体的设计，每个核苷酸结合状态需要一个独特的自由能最小值。