Trivedi Omita A, Arora Pooja, Vats Archana, Ansari Mohd Zeeshan, Tickoo Rashmi, Sridharan Vijayalakshmi, Mohanty Debasisa, Gokhale Rajesh S
National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi 110 067, India.
Mol Cell. 2005 Mar 4;17(5):631-43. doi: 10.1016/j.molcel.2005.02.009.
Mycobacterium tuberculosis cell envelope is a treasure house of biologically active lipids of fascinating molecular architecture. Although genetic studies have alluded to an array of genes in biosynthesis of complex lipids, their mechanistic, structural, and biochemical principles have not been investigated. Here, we have dissected the molecular logic underlying the biosynthesis of a virulence lipid phthiocerol dimycocerosate (PDIM). Cell-free reconstitution studies demonstrate that polyketide synthases, which are usually involved in the biosynthesis of secondary metabolites, are responsible for generating complex lipids in mycobacteria. We show that PapA5 protein directly transfers the protein bound mycocerosic acid analogs on phthiocerol to catalyze the final esterification step. Based on precise identification of biological functions of proteins from Pps cluster, we have rationally produced a nonmethylated variant of mycocerosate esters. Apart from elucidating mechanisms that generate chemical heterogeneity with PDIMs, this study also presents an attractive approach to explore host-pathogen interactions by altering mycobacterial surface coat.
结核分枝杆菌的细胞包膜是一个充满具有迷人分子结构的生物活性脂质的宝库。尽管遗传学研究已经提及了一系列参与复杂脂质生物合成的基因，但它们的机制、结构和生化原理尚未得到研究。在此，我们剖析了毒力脂质结核硬脂酸双分枝菌酸酯（PDIM）生物合成背后的分子逻辑。无细胞重建研究表明，通常参与次生代谢物生物合成的聚酮合酶负责在分枝杆菌中生成复杂脂质。我们发现PapA5蛋白直接将与蛋白质结合的分枝菌酸类似物转移到结核硬脂醇上，以催化最后的酯化步骤。基于对来自Pps簇的蛋白质生物学功能的精确鉴定，我们合理地制备了一种非甲基化的分枝菌酸酯变体。除了阐明产生具有化学异质性的PDIMs的机制外，本研究还提出了一种通过改变分枝杆菌表面包膜来探索宿主-病原体相互作用的有吸引力的方法。
