Hefei National Laboratory for Physical Sciences at the Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China.
School of Chemistry and Materials Science, University of Science and Technology of China, Hefei, Anhui, China.
mBio. 2020 Mar 17;11(2):e02749-19. doi: 10.1128/mBio.02749-19.
The wall teichoic acid (WTA) is a major cell wall component of Gram-positive bacteria, such as methicillin-resistant (MRSA), a common cause of fatal clinical infections in humans. Thus, the indispensable ABC transporter TarGH, which flips WTA from cytoplasm to extracellular space, becomes a promising target of anti-MRSA drugs. Here, we report the 3.9-Å cryo-electron microscopy (cryo-EM) structure of a 50% sequence-identical homolog of TarGH from at an ATP-free and inward-facing conformation. Structural analysis combined with activity assays enables us to clearly decode the binding site and inhibitory mechanism of the anti-MRSA inhibitor Targocil, which targets TarGH. Moreover, we propose a "crankshaft conrod" mechanism utilized by TarGH, which can be applied to similar ABC transporters that translocate a rather big substrate through relatively subtle conformational changes. These findings provide a structural basis for the rational design and optimization of antibiotics against MRSA. The wall teichoic acid (WTA) is a major component of cell wall and a pathogenic factor in methicillin-resistant (MRSA). The ABC transporter TarGH is indispensable for flipping WTA precursor from cytoplasm to the extracellular space, thus making it a promising drug target for anti-MRSA agents. The 3.9-Å cryo-EM structure of a TarGH homolog helps us to decode the binding site and inhibitory mechanism of a recently reported inhibitor, Targocil, and provides a structural platform for rational design and optimization of potential antibiotics. Moreover, we propose a "crankshaft conrod" mechanism to explain how a big substrate is translocated through subtle conformational changes of type II exporters. These findings advance our understanding of anti-MRSA drug design and ABC transporters.
壁磷壁酸（WTA）是革兰氏阳性菌（如耐甲氧西林金黄色葡萄球菌，MRSA）的主要细胞壁成分，是导致人类致命临床感染的常见原因。因此，不可或缺的 ABC 转运蛋白 TarGH 将 WTA 从细胞质翻转到细胞外空间，成为抗 MRSA 药物的有前途的靶标。在这里，我们报告了来自 的 TarGH 50%序列相同同源物在无 ATP 和内向构象下的 3.9Å 冷冻电镜（cryo-EM）结构。结构分析结合活性测定使我们能够清楚地解码抗 MRSA 抑制剂 Targocil 的结合位点和抑制机制，该抑制剂靶向 TarGH。此外，我们提出了 TarGH 利用的“曲柄连杆”机制，该机制可应用于通过相对细微的构象变化转运相当大的底物的类似 ABC 转运蛋白。这些发现为针对 MRSA 的抗生素的合理设计和优化提供了结构基础。壁磷壁酸（WTA）是细胞壁的主要成分，也是耐甲氧西林金黄色葡萄球菌（MRSA）的致病因素。ABC 转运蛋白 TarGH 对于将 WTA 前体从细胞质翻转到细胞外空间是必不可少的，因此成为抗 MRSA 药物的有前途的靶标。TarGH 同源物的 3.9Å 冷冻电镜结构有助于我们解码最近报道的抑制剂 Targocil 的结合位点和抑制机制，并为潜在抗生素的合理设计和优化提供了结构平台。此外，我们提出了一种“曲柄连杆”机制来解释如何通过 II 型外排泵的细微构象变化来转运大底物。这些发现提高了我们对抗 MRSA 药物设计和 ABC 转运蛋白的理解。
