Ntreh Abigail T, Weeks Jon W, Nickels Logan M, Zgurskaya Helen I
University of Oklahoma, Department of Chemistry and Biochemistry, Norman, Oklahoma, USA.
University of Oklahoma, Department of Chemistry and Biochemistry, Norman, Oklahoma, USA
J Bacteriol. 2016 Nov 4;198(23):3176-3185. doi: 10.1128/JB.00535-16. Print 2016 Dec 1.
TriABC-OpmH is an efflux pump from Pseudomonas aeruginosa with an unusual substrate specificity and protein composition. When overexpressed, this pump confers a high level of resistance to the biocide triclosan and the detergent SDS, which are commonly used in combinations for antimicrobial treatments. This activity requires an RND transporter (TriC), an outer membrane channel (OpmH), and two periplasmic membrane fusion proteins (TriA and TriB) with nonequivalent functions. In the active complex, TriA is responsible for the recruitment of OpmH, while TriB is responsible for stimulation of the transporter TriC. Here, we used the functional and structural differences between the two membrane fusion proteins to link their functional roles to specific interactions with OpmH. Our results provide evidence that the TriB-dependent stimulation of the TriC transporter is coupled to opening of the OpmH aperture through binding to the interprotomer groove of OpmH.
Multidrug efflux transporters are important contributors to intrinsic and acquired antibiotic resistance in clinics. In Gram-negative bacteria, these transporters have a characteristic tripartite architecture spanning the entire two-membrane cell envelope. How such complexes are assembled and how the reactions separated in two different membranes are coupled to provide efficient efflux of various compounds across the cell envelope remain unclear. This study addressed these questions, and the results suggest a mechanism for functional integration of drug efflux by the inner membrane transporter and opening of the channel for transport across the outer membrane.
TriABC - OpmH是铜绿假单胞菌的一种外排泵，具有不同寻常的底物特异性和蛋白质组成。当该泵过度表达时，会赋予对杀菌剂三氯生和去污剂十二烷基硫酸钠的高水平抗性，这两种物质常用于联合抗菌治疗。这种活性需要一个RND转运蛋白（TriC）、一个外膜通道（OpmH）以及两个功能不等同的周质膜融合蛋白（TriA和TriB）。在活性复合物中，TriA负责招募OpmH，而TriB负责刺激转运蛋白TriC。在此，我们利用这两种膜融合蛋白之间的功能和结构差异，将它们的功能作用与和OpmH的特定相互作用联系起来。我们的结果提供了证据，表明TriB对TriC转运蛋白的刺激通过与OpmH的原体间凹槽结合而与OpmH孔道的开放相偶联。
多药外排转运蛋白是临床中固有和获得性抗生素耐药性的重要促成因素。在革兰氏阴性菌中，这些转运蛋白具有跨越整个双膜细胞包膜的特征性三方结构。这种复合物是如何组装的，以及在两个不同膜中分开的反应是如何偶联以实现各种化合物有效跨细胞包膜外排的，目前仍不清楚。本研究解决了这些问题，结果提示了一种内膜转运蛋白介导药物外排功能整合以及外膜转运通道开放的机制。
