Sumyk Manuela, Himpich Stephanie, Foong Wuen Ee, Herrmann Andrea, Pos Klaas M, Tam Heng-Keat
Institute of Biochemistry, Goethe-University Frankfurt, Frankfurt, Germany.
Front Microbiol. 2021 Jul 19;12:711158. doi: 10.3389/fmicb.2021.711158. eCollection 2021.
is an important nosocomial pathogen that requires thoughtful consideration in the antibiotic prescription strategy due to its multidrug resistant phenotype. Tetracycline antibiotics have recently been re-administered as part of the combination antimicrobial regimens to treat infections caused by . We show that the TetA(G) efflux pump of AYE confers resistance to a variety of tetracyclines including the clinically important antibiotics doxycycline and minocycline, but not to tigecycline. Expression of gene is regulated by the TetR repressor of AYE (AbTetR). Thermal shift binding experiments revealed that AbTetR preferentially binds tetracyclines which carry a O-5H moiety in ring B, whereas tetracyclines with a 7-dimethylamino moiety in ring D are less well-recognized by AbTetR. Confoundingly, tigecycline binds to AbTetR even though it is not transported by TetA(G) efflux pump. Structural analysis of the minocycline-bound AbTetR-Gln116Ala variant suggested that the non-conserved Arg135 interacts with the ring D of minocycline by cation-π interaction, while the invariant Arg104 engages in H-bonding with the O-11H of minocycline. Interestingly, the Arg135Ala variant exhibited a binding preference for tetracyclines with an unmodified ring D. In contrast, the Arg104Ala variant preferred to bind tetracyclines which carry a O-6H moiety in ring C except for tigecycline. We propose that Arg104 and Arg135, which are embedded at the entrance of the AbTetR binding pocket, play important roles in the recognition of tetracyclines, and act as a barrier to prevent the release of tetracycline from its binding pocket upon AbTetR activation. The binding data and crystal structures obtained in this study might provide further insight for the development of new tetracycline antibiotics to evade the specific efflux resistance mechanism deployed by .
是一种重要的医院病原体，由于其多重耐药表型，在抗生素处方策略中需要深思熟虑。四环素类抗生素最近已重新用于联合抗菌治疗方案，以治疗由引起的感染。我们发现AYE菌株的TetA(G)外排泵赋予对多种四环素的抗性，包括临床上重要的抗生素强力霉素和米诺环素，但对替加环素无抗性。AYE菌株（AbTetR）的TetR阻遏物调节基因的表达。热迁移结合实验表明，AbTetR优先结合在B环带有O-5H基团的四环素，而在D环带有7-二甲基氨基基团的四环素则较少被AbTetR识别。令人困惑的是，替加环素虽不被TetA(G)外排泵转运，但能与AbTetR结合。米诺环素结合的AbTetR-Gln116Ala变体的结构分析表明，非保守的Arg135通过阳离子-π相互作用与米诺环素的D环相互作用，而不变的Arg104与米诺环素的O-11H形成氢键。有趣的是，Arg135Ala变体对D环未修饰的四环素表现出结合偏好。相反，Arg104Ala变体更倾向于结合在C环带有O-6H基团的四环素（替加环素除外）。我们认为，位于AbTetR结合口袋入口处的Arg104和Arg135在四环素识别中起重要作用，并作为一道屏障，防止四环素在AbTetR激活时从其结合口袋释放。本研究获得的结合数据和晶体结构可能为开发新的四环素类抗生素以规避所采用的特定外排耐药机制提供进一步的见解。
