革兰阴性菌中合成Kdo2-Lipid A的蛋白质反应机理研究及抑制剂筛选

Kdo2-Lipid A(Lipid A)是革兰阴性菌脂多糖LPS的关键活性成分，具有将脂多糖固定在外膜外表面的锚定作用，不仅是革兰阴性菌内毒素的活性实体，同时也是革兰阴性菌生存的必需因子，抑制合成Lipid A蛋白质组的活性会导致革兰阴性菌死亡。由于这些蛋白质与现有革兰阴性菌抗菌剂的作用靶点完全不同，将会成为新型抗菌剂开发的突破点。本申请，以合成Lipid A的蛋白质组中未知的，膜表面存在的LpxH、LpxB及因基质较小而成为抗菌剂开发重点的LpxC为研究对象，X射线结晶结构分析作为主要研究手段，阐明这些蛋白质的基质识别及合成反应作用机理。并基于所得到的3种蛋白质及蛋白质与基质/产物复合体的立体结构，从天然药物有效活性成分中筛选和寻找LpxC、LpxH、LpxB的抑制剂，为新型抗革兰阴性菌药物开发提供先导化合物。

Lipid A which is the key component of lipopolysaccharide (LPS) and serves as an outer membrane anchor is an essential factor for the survival of Gram-negative bacteria, and responsible for major bioactivity of endotoxin. Lipid A biosynthesis requires nine enzymes which can be the potential agent targets for the new drug discovery since they are different targets with that of the current antibacterial agents. Therefore the study on the Lipid A biosynthetic enzymes in the molecular level is the important topic in the field of medical and biological science. This project focus on three Lipid A biosynthetic enzymes (LpxC, LpxH and LpxB), which are located closed to membrane or inner membrane. We will reveal the substrate recognition and reaction mechanisms of LpxH and LpxB by crystal structure analysis in the apo form and the complex with substrate or product. Furthermore, we will search active compounds which are able to inhibit the Lipid A biosynthesis of LpxC, LpxH and LpxB, from natural product/drug of herbal medicine for discovering lead/hint ligands of new antibacterial agents.