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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Dynamics of α-helical subdomain rotation in the intact maltose ATP-binding cassette transporter
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Dynamics of α-helical subdomain rotation in the intact maltose ATP-binding cassette transporter

机译：完整的麦芽糖ATP结合盒转运蛋白中α螺旋亚域旋转的动力学。

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摘要

ATP-binding cassette (ABC) transporters are powered by a nucleo-tide-binding domain dimer that opens and closes during cycles of ATP hydrolysis. These domains consist of a RecA-like subdomain and an a-helical subdomain that is specific to the family. Many studies on isolated domains suggest that the helical subdomain rotates toward the RecA-like subdomain in response to ATP binding, moving the family signature motif into a favorable position to interact with the nucleotide across the dimer interface. Moreover, the transmembrane domains are docked into a cleft at the interface between these subdomains, suggesting a putative role of the rotation in interdomain communication. Electron paramagnetic resonance spectroscopy was used to study the dynamics of this rotation in the intact Escherichia coli maltose transporter MalFGK2. This importer requires a periplasmic maltose-binding protein (MBP) that activates ATP hydrolysis by promoting the closure of the cassette dimer (MalK2). Whereas this rotation occurred during the transport cycle, it required not only trinucleotide, but also MBP, suggesting it is part of a global conformational change in the transporter. Interaction of AMP-PNP-Mg2+ and a MBP that is locked in a closed conformation induced a transition from open MalK2 to semiopen MalK2 without significant subdomain rotation. Inward rotation of the helical subdomain and complete closure of MalK2 therefore appear to be coupled to the reorientation of transmembrane helices and the opening of MBP, events that promote transfer of maltose into the transporter. After ATP hydrolysis, the helical subdomain rotates out as MalK2 opens, resetting the transporter in an inward-facing conformation.
机译：ATP结合盒（ABC）转运蛋白由核苷酸结合结构域二聚体提供动力，该二聚体在ATP水解周期中打开和关闭。这些域由类似RecA的子域和特定于该家族的a螺旋子域组成。关于隔离域的许多研究表明，螺旋形子域响应于ATP结合而向着RecA样子域旋转，从而将家族签名基序移到了一个有利位置，可通过二聚体界面与核苷酸相互作用。此外，跨膜结构域在这些子结构域之间的界面处停靠在裂缝中，表明旋转在域间通信中具有假定的作用。电子顺磁共振波谱用于研究完整的麦芽糖转运蛋白MalFGK2中这种旋转的动力学。该进口商需要周质麦芽糖结合蛋白（MBP），该蛋白通过促进盒二聚体（MalK2）的闭合来激活ATP水解。尽管这种旋转发生在转运周期中，但它不仅需要三核苷酸，还需要MBP，这表明它是转运蛋白整体构象变化的一部分。 AMP-PNP-Mg2 +和MBP的相互作用被锁定在一个封闭的构象中，诱导了从开放MalK2到半开放MalK2的过渡，而没有明显的亚域旋转。因此，螺旋亚结构域的向内旋转和MalK2的完全闭合似乎与跨膜螺旋的重新定向和MBP的打开有关，这些事件促进了麦芽糖向转运蛋白的转移。 ATP水解后，随着MalK2打开，螺旋亚结构域旋转出去，从而将转运蛋白重置为向内构象。

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