Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853.
Department of Chemistry, University of Houston, Houston, TX 77204.
Proc Natl Acad Sci U S A. 2017 Jun 27;114(26):6694-6699. doi: 10.1073/pnas.1704729114. Epub 2017 Jun 12.
Multicomponent efflux complexes constitute a primary mechanism for Gram-negative bacteria to expel toxic molecules for survival. As these complexes traverse the periplasm and link inner and outer membranes, it remains unclear how they operate efficiently without compromising periplasmic plasticity. Combining single-molecule superresolution imaging and genetic engineering, we study in living cells the tripartite efflux complex CusCBA of the resistance-nodulation-division family that is essential for bacterial resistance to drugs and toxic metals. We find that CusCBA complexes are dynamic structures and shift toward the assembled form in response to metal stress. Unexpectedly, the periplasmic adaptor protein CusB is a key metal-sensing element that drives the assembly of the efflux complex ahead of the transcription activation of the operon for defending against metals. This adaptor protein-mediated dynamic pump assembly allows the bacterial cell for efficient efflux upon cellular demand while still maintaining periplasmic plasticity; this could be broadly relevant to other multicomponent efflux systems.
多组分外排复合物是革兰氏阴性菌排出毒性分子以维持生存的主要机制。由于这些复合物穿过周质并连接内膜和外膜，因此它们在不损害周质可塑性的情况下如何高效运作仍不清楚。通过结合单分子超分辨率成像和遗传工程，我们在活细胞中研究了耐药-结节-分裂家族的三联外排复合物 CusCBA，该复合物对于细菌对抗药物和有毒金属的抵抗力至关重要。我们发现 CusCBA 复合物是动态结构，并且会响应金属应激而向组装形式转变。出人意料的是，周质衔接蛋白 CusB 是一个关键的金属感应元件，它在操纵子的转录激活之前驱动外排复合物的组装，以抵御金属。这种衔接蛋白介导的动态泵组装允许细菌细胞在细胞需要时进行有效的外排，同时仍保持周质的可塑性；这可能与其他多组分外排系统广泛相关。
