The MexJK efflux pump of Pseudomonas aeruginosa requires OprM for antibiotic efflux but not for efflux of triclosan
The MexJK efflux pump of Pseudomonas aeruginosa requires OprM for antibiotic efflux but not for efflux of triclosan
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DOI：
10.1128/jb.184.18.5036-5044.2002
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发表时间：
2002-09-01
影响因子：
3.2
通讯作者：
Schweizer, HP
中科院分区：
文献类型：
--
作者：
Chuanchuen, R;Narasaki, CT;Schweizer, HP
使用杀菌剂三氯生作为选择剂，分离出敏感铜绿假单胞菌菌株的几个三氯生抗性突变体。从这些突变体之一赋予三氯生抗性的DNA片段的克隆和表征揭示了迄今为止未表征的抗性诱导细胞分裂（RND）家族的外排系统，其被命名为MexJK，并由mexJK操纵子编码。该操纵子的表达受mexL的产物负调控，mexL是位于mexJK上游并从mexJK转录的基因。三氯生抗性突变体包含一个单核苷酸的变化，在MexL，这导致了一个氨基酸的变化，在推定的螺旋-转角-螺旋结构域的MexL。MexL蛋白属于TetR家族的阻遏蛋白。MexJK系统流出四环素和红霉素，但仅在外膜蛋白通道OprM的存在下; OprJ和OprN与MexJK不起作用。三氯生外排既不需要测试的外膜蛋白通道，但需要MexJ膜融合蛋白和MexK内膜RND转运蛋白。本研究的结果表明，MexJK可能作为三氯生外排的双组分RND泵发挥作用，但必须与OprM结合形成三方抗生素外排系统。此外，结果证实三氯生是研究RND多药外排系统的极好工具，因此这种流行的杀生物剂很容易选择与抗生素交叉耐药的突变体。
Using the biocide triclosan as a selective agent, several triclosan-resistant mutants of a susceptible Pseudomonas aeruginosa strain were isolated. Cloning and characterization of a DNA fragment conferring triclosan resistance from one of these mutants revealed a hitherto uncharacterized efflux system of the resistance nodulation cell division (RND) family, which was named MexJK and which is encoded by the mexJK operon. Expression of this operon is negatively regulated by the product of mexL, a gene located upstream of and transcribed divergently from mexJK. The triclosan-resistant mutant contained a single nucleotide change in mexL, which caused an amino acid change in the putative helix-turn-helix domain of MexL. The MexL protein belongs to the TetR family of repressor proteins. The MexJK system effluxed tetracycline and erythromycin but only in the presence of the outer membrane protein channel OprM; OprJ and OprN did not function with MexJK. Triclosan efflux required neither of the outer membrane protein channels tested but necessitated the MexJ membrane fusion protein and the MexK inner membrane RND transporter. The results presented in this study suggest that MexJK may function as a two-component RND pump for triclosan efflux but must associate with OprM to form a tripartite antibiotic efflux system. Furthermore, the results confirm that triclosan is an excellent tool for the study of RND multidrug efflux systems and that this popular biocide therefore readily selects mutants which are cross-resistant with antibiotics.