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首页> 外文期刊>Journal of Molecular Biology >Analysis of the isolated SecA DEAD motor suggests a mechanism for chemical-mechanical coupling.
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Analysis of the isolated SecA DEAD motor suggests a mechanism for chemical-mechanical coupling.

机译：对隔离的SecA DEAD电动机的分析提出了一种化学机械耦合的机制。

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摘要

The preprotein cross-linking domain and C-terminal domains of Escherichia coli SecA were removed to create a minimal DEAD motor, SecA-DM. SecA-DM hydrolyzes ATP and has the same affinity for ADP as full-length SecA. The crystal structure of SecA-DM in complex with ADP was solved and shows the DEAD motor in a closed conformation. Comparison with the structure of the E. coli DEAD motor in an open conformation (Protein Data Bank ID 2FSI) indicates main-chain conformational changes in two critical sequences corresponding to Motif III and Motif V of the DEAD helicase family. The structures that the Motif III and Motif V sequences adopt in the DEAD motor open conformation are incompatible with the closed conformation. Therefore, when the DEAD motor makes the transition from open to closed, Motif III and Motif V are forced to change their conformations, which likely functions to regulate passage through the transition state for ATP hydrolysis. The transition state for ATP hydrolysis for the SecA DEAD motor was modeled based on the conformation of the Vasa helicase in complex with adenylyl imidodiphosphate and RNA (Protein Data Bank ID 2DB3). A mechanism for chemical-mechanical coupling emerges, where passage through the transition state for ATP hydrolysis is hindered by the conformational changes required in Motif III and Motif V, and may be promoted by binding interactions with the preprotein substrate and/or other translocase domains and subunits.
机译：去除大肠杆菌SecA的前蛋白交联结构域和C末端结构域，以创建最小的DEAD马达SecA-DM。 SecA-DM水解ATP，并且对ADP的亲和力与全长SecA相同。解决了SecA-DM与ADP形成复合物的晶体结构，并显示了DEAD电机处于封闭状态。与开放构象（蛋白质数据库ID 2FSI）中的大肠杆菌DEAD马达的结构比较表明，在对应于DEAD解旋酶家族的Motif III和Motif V的两个关键序列中主链构象变化。 DEAD马达开放构象中Motif III和Motif V序列采用的结构与封闭构象不兼容。因此，当DEAD电机从打开状态转换为关闭状态时，Motif III和Motif V被迫改变其构象，这很可能起到调节通过过渡态进行ATP水解的作用。 SecA DEAD电机的ATP水解过渡态是基于瓦萨解旋酶与腺苷二酰亚胺二磷酸和RNA（蛋白质数据库ID 2DB3）复合的构象而建模的。出现了一种化学机械耦合的机制，其中通过Motif III和Motif V所需的构象变化来阻止通过ATP水解的过渡状态，并且可以通过与前蛋白底物和/或其他转位酶结构域和亚单位。

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