Xu Yanyan, Seelig Anna, Bernèche Simon
SIB Swiss Institute of Bioinformatics, Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland; Biozentrum, University of Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland.
Biozentrum, University of Basel , Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland.
ACS Cent Sci. 2017 Mar 22;3(3):250-258. doi: 10.1021/acscentsci.7b00068. Epub 2017 Mar 7.
ATP-binding cassette (ABC) transporters use the energy of ATP binding and hydrolysis to move a large variety of compounds across biological membranes. P-glycoprotein, involved in multidrug resistance, is the most investigated eukaryotic family member. Although a large number of biochemical and structural approaches have provided important information, the conformational dynamics underlying the coupling between ATP binding/hydrolysis and allocrite transport remains elusive. To tackle this issue, we performed molecular dynamic simulations for different nucleotide occupancy states of Sav1866, a prokaryotic P-glycoprotein homologue. The simulations reveal an outward-closed conformation of the transmembrane domain that is stabilized by the binding of two ATP molecules. The hydrolysis of a single ATP leads the X-loop, a key motif of the ATP binding cassette, to interfere with the transmembrane domain and favor its outward-open conformation. Our findings provide a structural basis for the unidirectionality of transport in ABC exporters and suggest a ratio of one ATP hydrolyzed per transport cycle.
ATP结合盒（ABC）转运蛋白利用ATP结合和水解产生的能量，将多种化合物转运穿过生物膜。参与多药耐药的P-糖蛋白是研究最多的真核生物家族成员。尽管大量的生化和结构方法提供了重要信息，但ATP结合/水解与变构配体转运之间偶联的构象动力学仍不清楚。为了解决这个问题，我们对原核P-糖蛋白同源物Sav1866的不同核苷酸占据状态进行了分子动力学模拟。模拟结果揭示了跨膜结构域的向外关闭构象，该构象通过两个ATP分子的结合而稳定。单个ATP的水解导致ATP结合盒的关键基序X环干扰跨膜结构域，并有利于其向外开放构象。我们的研究结果为ABC转运蛋白单向运输提供了结构基础，并表明每个运输循环水解一个ATP的比例。
