Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
J Biol Chem. 2022 Oct;298(10):102473. doi: 10.1016/j.jbc.2022.102473. Epub 2022 Sep 9.
WalKR is a two-component system that is essential for viability in Gram-positive bacteria that regulates the all-important autolysins in cell wall homeostasis. Further investigation of this essential system is important for identifying ways to address antibiotic resistance. Here, we show that a T101M mutation in walR confers a defect in autolysis, a thickened cell wall, and decreased susceptibility to antibiotics that target lipid II cycle, a phenotype that is reminiscent of the clinical resistance form known as vancomycin intermediate-resistant Staphylococcus aureus. Importantly, this is accompanied by dramatic sensitization to tunicamycin. We demonstrate that this phenotype is due to partial collapse of a pathway consisting of autolysins, AtlA and Sle1, a transmembrane sugar permease, MurP, and GlcNAc recycling enzymes, MupG and MurQ. We suggest that this causes a shortage of substrate for the peptidoglycan biosynthesis enzyme MraY, causing it to be hypersensitive to competitive inhibition by tunicamycin. In conclusion, our results constitute a new molecular model for antibiotic sensitivity in S. aureus and a promising new route for antibiotic discovery.
WalKR 是革兰氏阳性菌中必需的双组份系统，可调节细胞壁动态平衡中至关重要的自溶素。进一步研究这个必需系统对于寻找解决抗生素耐药性的方法非常重要。在这里，我们发现 walR 中的 T101M 突变导致自溶缺陷、细胞壁增厚和对靶向脂质 II 循环的抗生素的敏感性降低，这种表型类似于临床耐药形式的万古霉素中介耐金黄色葡萄球菌。重要的是，这伴随着对衣霉素的显著增敏作用。我们证明这种表型是由于由自溶素 AtlA 和 Sle1、跨膜糖渗透酶 MurP 以及 GlcNAc 循环酶 MupG 和 MurQ 组成的途径部分崩溃所致。我们认为这导致了肽聚糖生物合成酶 MraY 的底物短缺，使其对衣霉素的竞争性抑制作用变得敏感。总之，我们的结果构成了金黄色葡萄球菌抗生素敏感性的新分子模型，为抗生素发现提供了有希望的新途径。
