Mishra Smriti, Verhalen Brandy, Stein Richard A, Wen Po-Chao, Tajkhorshid Emad, Mchaourab Hassane S
Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, United States.
Department of Biochemistry, College of Medicine, University of Illinois, Urbana, United States Center for Biophysics and Computational Biology, University of Illinois, Urbana, United States The Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana, Unites States.
Elife. 2014 May 16;3:e02740. doi: 10.7554/eLife.02740.
Multidrug ATP binding cassette (ABC) exporters are ubiquitous ABC transporters that extrude cytotoxic molecules across cell membranes. Despite recent progress in structure determination of these transporters, the conformational motion that transduces the energy of ATP hydrolysis to the work of substrate translocation remains undefined. Here, we have investigated the conformational cycle of BmrCD, a representative of the heterodimer family of ABC exporters that have an intrinsically impaired nucleotide binding site. We measured distances between pairs of spin labels monitoring the movement of the nucleotide binding (NBD) and transmembrane domains (TMD). The results expose previously unobserved structural intermediates of the NBDs arising from asymmetric configuration of catalytically inequivalent nucleotide binding sites. The two-state transition of the TMD, from an inward- to an outward-facing conformation, is driven exclusively by ATP hydrolysis. These findings provide direct evidence of divergence in the mechanism of ABC exporters.DOI: http://dx.doi.org/10.7554/eLife.02740.001.
多药ATP结合盒（ABC）转运蛋白是一类普遍存在的ABC转运体，可将细胞毒性分子跨细胞膜排出。尽管最近在这些转运体的结构测定方面取得了进展，但将ATP水解能量转化为底物转运功的构象运动仍不明确。在这里，我们研究了BmrCD的构象循环，BmrCD是ABC转运蛋白异二聚体家族的代表，其核苷酸结合位点存在内在缺陷。我们测量了监测核苷酸结合（NBD）和跨膜结构域（TMD）运动的自旋标记对之间的距离。结果揭示了由催化不等价核苷酸结合位点的不对称构型产生的NBD以前未观察到的结构中间体。TMD从内向构象到外向构象的双态转变完全由ATP水解驱动。这些发现为ABC转运蛋白机制的差异提供了直接证据。DOI: http://dx.doi.org/10.7554/eLife.02740.001 。
