Corbett Kevin D, Berger James M
Department of Molecular and cellular biology, University of California, Berkeley, California 94720, USA.
Structure. 2005 Jun;13(6):873-82. doi: 10.1016/j.str.2005.03.013.
GHL proteins are functionally diverse enzymes defined by the presence of a conserved ATPase domain that self-associates to trap substrate upon nucleotide binding. The structural states adopted by these enzymes during nucleotide hydrolysis and product release, and their consequences for enzyme catalysis, have remained unclear. Here, we have determined a complete structural map of the ATP turnover cycle for topoVI-B, the ATPase subunit of the archaeal GHL enzyme topoisomerase VI. With this ensemble of structures, we show that significant conformational changes in the subunit occur first upon ATP binding, and subsequently upon release of hydrolyzed P(i). Together, these data provide a structural framework for understanding the role of ATP hydrolysis in the type II topoisomerase reaction. Our results also suggest that the GHL ATPase module is a molecular switch in which ATP hydrolysis serves as a prerequisite but not a driving force for substrate-dependent structural transitions in the enzyme.
GHL蛋白是功能多样的酶，其特征在于存在一个保守的ATP酶结构域，该结构域在核苷酸结合时会自我缔合以捕获底物。这些酶在核苷酸水解和产物释放过程中所采用的结构状态及其对酶催化的影响仍不清楚。在这里，我们确定了古细菌GHL酶拓扑异构酶VI的ATP酶亚基topoVI-B的ATP周转循环的完整结构图谱。通过这一系列结构，我们表明亚基中的显著构象变化首先发生在ATP结合时，随后发生在水解的P(i)释放时。这些数据共同提供了一个结构框架，用于理解ATP水解在II型拓扑异构酶反应中的作用。我们的结果还表明，GHL ATP酶模块是一个分子开关，其中ATP水解是酶中底物依赖性结构转变的前提条件，但不是驱动力。
