School of Medicine and School of Biochemistry and Immunology, Trinity College Dublin, Dublin D02 R590, Ireland.
Department of Chemical and Structural Biology, Weizmann Institute of Science, Rehovot 7610001, Israel.
Sci Adv. 2023 Jun 30;9(26):eadf5799. doi: 10.1126/sciadv.adf5799.
Bacterial lipoproteins (BLPs) decorate the surface of membranes in the cell envelope. They function in membrane assembly and stability, as enzymes, and in transport. The final enzyme in the BLP synthesis pathway is the apolipoprotein -acyltransferase, Lnt, which is proposed to act by a ping-pong mechanism. Here, we use x-ray crystallography and cryo-electron microscopy to chart the structural changes undergone during the progress of the enzyme through the reaction. We identify a single active site that has evolved to bind, individually and sequentially, substrates that satisfy structural and chemical criteria to position reactive parts next to the catalytic triad for reaction. This study validates the ping-pong mechanism, explains the molecular bases for Lnt's substrate promiscuity, and should facilitate the design of antibiotics with minimal off-target effects.
细菌脂蛋白 (BLPs) 装饰在细胞膜的表面。它们在膜的组装和稳定性、作为酶以及在运输中发挥功能。BLP 合成途径中的最后一种酶是载脂蛋白酰基转移酶 Lnt，其被认为通过乒乓机制发挥作用。在这里，我们使用 X 射线晶体学和 cryo-electron microscopy 来描绘酶在反应过程中经历的结构变化。我们确定了一个单一的活性位点，该位点进化到可以单独且依次结合满足结构和化学标准的底物，将反应性部分定位在催化三联体旁边以进行反应。这项研究验证了乒乓机制，解释了 Lnt 底物混杂性的分子基础，并且应该有助于设计具有最小脱靶效应的抗生素。
