Jones Peter M, George Anthony M
Department of Cell and Molecular Biology, University of Technology Sydney, P.O. Box 123 Broadway, Sydney NSW 2007, Australia.
Proc Natl Acad Sci U S A. 2002 Oct 1;99(20):12639-44. doi: 10.1073/pnas.152439599. Epub 2002 Sep 17.
ATP-binding cassette (ABC) transporters are membrane-bound molecular pumps that form one of the largest of all protein families. Several of them are central to phenomena of biomedical interest, including cystic fibrosis and resistance to chemotherapeutic drugs. ABC transporters share a common architecture comprising two hydrophilic nucleotide-binding domains (NBDs) and two hydrophobic transmembrane domains (TMDs) that form the substrate pathway across the membrane. The conformational changes in the NBDs induced by ATP hydrolysis and the means by which they are transmitted to the TMDs to effect substrate translocation remain largely unknown. We have performed a molecular dynamics simulation of HisP, the well studied NBD of the bacterial histidine permease, to identify hinges and switches of the NBD conformational transitions and subunit-subunit interfaces. This analysis reveals that the TMDs regulate ATP hydrolysis by controlling conformational transitions of the NBD helical domains, and identifies the conformational changes and the crucial TMD:NBD interface, by which the energy of ATP hydrolysis is transmitted to the TMDs. We also define the conformational transitions of the Q-loop, a key element of the NBD mechanism, and identify pathways by which Q-loop switching is coordinated with TMD and NBD conformational changes. We propose a model for the catalytic cycle of ABC transporters that shows how substrate-binding and transport by the TMDs may be coordinated and coupled with ATP binding and hydrolysis in the NBDs.
ATP结合盒（ABC）转运蛋白是膜结合分子泵，构成了所有蛋白质家族中最大的家族之一。其中一些对于生物医学关注的现象至关重要，包括囊性纤维化和对化疗药物的耐药性。ABC转运蛋白具有共同的结构，包括两个亲水性核苷酸结合结构域（NBDs）和两个疏水性跨膜结构域（TMDs），它们形成了跨膜的底物通道。由ATP水解诱导的NBDs构象变化以及它们传递到TMDs以实现底物转运的方式在很大程度上仍然未知。我们对细菌组氨酸通透酶中经过充分研究的NBD HisP进行了分子动力学模拟，以确定NBD构象转变的铰链和开关以及亚基-亚基界面。该分析表明，TMDs通过控制NBD螺旋结构域的构象转变来调节ATP水解，并确定了构象变化以及关键的TMD:NBD界面，通过该界面ATP水解的能量传递到TMDs。我们还定义了NBD机制的关键元件Q环的构象转变，并确定了Q环开关与TMD和NBD构象变化协调的途径。我们提出了一个ABC转运蛋白催化循环的模型，该模型展示了TMDs的底物结合和转运如何与NBDs中的ATP结合和水解相协调和偶联。
