A Novel Interaction Linking the FAS-II and Phthiocerol Dimycocerosate (PDIM) Biosynthetic Pathways
A Novel Interaction Linking the FAS-II and Phthiocerol Dimycocerosate (PDIM) Biosynthetic Pathways
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DOI：
10.1074/jbc.m802169200
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发表时间：
2008-11-14
影响因子：
4.8
通讯作者：
Tonge, Peter J.
中科院分区：
文献类型：
--
作者：
Kruh, Nicole A.;Borgaro, Janine G.;Tonge, Peter J.
结核分枝杆菌中的脂肪酸生物合成（FAS-II）途径产生长链脂肪酸，所述长链脂肪酸充当分枝杆菌酸（分枝杆菌细胞壁的必需组分）的前体。认为FAS-II途径中的酶在细胞内形成一种或多种非共价多酶复合物，并且使用细菌双杂交筛选来搜索途径中缺失的组分，并提供关于涉及这些酶的体内相互作用的额外数据。以FAS-Ⅱ β-酮脂酰合成酶KasA为诱饵，进行了广泛的细菌双杂交筛选。结核病基因组片段文库中意外地揭示了KasA和PpsB以及PpsD之间的新型相互作用，这两个聚酮模块参与毒力脂质邻苯二甲酸二酯（PDIM）的生物合成。序列分析表明，KasA相互作用与PpsB和PpsD在该地区的酰基载体结构域的每种蛋白质，提高了脂质可以转移之间的FAS-II和PDIM生物合成途径的可能性。利用纯化的蛋白质和放射性标记的脂质的后续研究揭示，加载到PpsB上的脂肪酸被转移到KasA中，并且还掺入到使用耻垢分枝杆菌裂解物合成的长链脂肪酸中。这些数据表明，除了产生PDIM之外，生长的邻苯二甲酸二苯酯产物还可以通过KasA作为进一步延伸的入口点穿梭到FAS-II途径中。这些生物合成途径之间的相互作用可能作为增加分枝杆菌脂质多样性、增强功能性和细胞壁整体复杂性的简单手段而存在。
The fatty acid biosynthesis (FAS-II) pathway in Mycobacterium tuberculosis generates long chain fatty acids that serve as the precursors to mycolic acids, essential components of the mycobacterial cell wall. Enzymes in the FAS-II pathway are thought to form one or more noncovalent multi-enzyme complexes within the cell, and a bacterial two-hybrid screen was used to search for missing components of the pathway and to furnish additional data on interactions involving these enzymes in vivo. Using the FAS-II beta-ketoacyl synthase, KasA, as bait, an extensive bacterial two-hybrid screen of a M. tuberculosis genome fragment library unexpectedly revealed a novel interaction between KasA and PpsB as well as PpsD, two polyketide modules involved in the biosynthesis of the virulence lipid phthiocerol dimycocerosate (PDIM). Sequence analysis revealed that KasA interacts with PpsB and PpsD in the region of the acyl carrier domain of each protein, raising the possibility that lipids could be transferred between the FAS-II and PDIM biosynthetic pathways. Subsequent studies utilizing purified proteins and radiolabeled lipids revealed that fatty acids loaded onto PpsB were transferred to KasA and also incorporated into long chain fatty acids synthesized using a Mycobacterium smegmatis lysate. These data suggest that in addition to producing PDIMs, the growing phthiocerol product can also be shuttled into the FAS-II pathway via KasA as an entry point for further elongation. Interactions between these biosynthetic pathways may exist as a simple means to increase mycobacterial lipid diversity, enhancing functionality and the overall complexity of the cell wall.