Identification of the required acyltransferase step in the biosynthesis of the phosphatidylinositol mannosides of Mycobacterium species
Identification of the required acyltransferase step in the biosynthesis of the phosphatidylinositol mannosides of Mycobacterium species
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DOI：
10.1074/jbc.m303639200
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发表时间：
2003-09-19
影响因子：
4.8
通讯作者：
Jackson, M
中科院分区：
文献类型：
--
作者：
Korduláková, J;Gilleron, M;Jackson, M
分枝杆菌的磷脂酰肌醇甘露糖苷（PIM）、脂甘露聚糖（LM）和脂阿拉伯甘露聚糖（LAM）的糖基化磷脂酰肌醇（GPI）锚的脂肪酰基功能在这些分子的物理性质和生物活性中起关键作用。在寻找酰化PIM，LM和LAM的GPI锚的酰基转移酶中，我们研究了分枝杆菌Rv 2611 c基因的功能，该基因编码参与磷脂酰肌醇甘露糖苷合成早期步骤的推定酰基转移酶。构建了耻垢分枝杆菌的Rv 2611 c突变体，其表现出严重的生长缺陷，并且与野生型亲本菌株相比，含有增加量的磷脂酰肌醇单-和二-甘露糖苷以及减少量的酰化磷脂酰肌醇二-甘露糖苷。在无细胞测定中，M.过表达M.结核Rv 2611 c基因将[C-14]棕榈酸酯掺入酰化的磷脂酰肌醇单-和二-甘露糖苷中，并且比来自野生型菌株的提取物更有效地将冷的内源性脂肪酸转移到C-14“-标记的磷脂酰肌醇单-和二-甘露糖苷上。从M.在这些方面，smegestion受到了极大的损害。这项工作提供了证据，证明Rv 2611 c是酰基转移酶，其催化磷脂酰肌醇单-和二-甘露糖苷中与肌醇的位置2连接的甘露糖残基的6-位置的酰化，其中单-甘露糖基化的脂质受体是酶的主要底物。我们还提供了第一个证据表明，两个不同的途径导致形成酰化PIM 2从PIM 1在分枝杆菌。
Fatty acyl functions of the glycosylated phosphatidylinositol (GPI) anchors of the phosphatidylinositol mannosides (PIM), lipomannan (LM), and lipoarabinomannan (LAM) of mycobacteria play a critical role in both the physical properties and biological activities of these molecules. In a search for the acyltransferases that acylate the GPI anchors of PIM, LM, and LAM, we examined the function of the mycobacterial Rv2611c gene that encodes a putative acyltransferase involved in the early steps of phosphatidylinositol mannoside synthesis. A Rv2611c mutant of Mycobacterium smegmatis was constructed which exhibited severe growth defects and contained an increased amount of phosphatidylinositol mono- and di-mannosides and a decreased amount of acylated phosphatidylinositol di-mannosides compared with the wild-type parental strain. In cell-free assays, extracts from M. smegmatis overexpressing the M. tuberculosis Rv2611c gene incorporated [C-14]palmitate into acylated phosphatidylinositol mono- and di-mannosides, and transferred cold endogenous fatty acids onto C-14''-labeled phosphatidylinositol mono- and di-mannosides more efficiently than extracts from the wild-type strain. Cell-free extracts from the Rv2611c mutant of M. smegmatis were greatly impaired in these respects. This work provides evidence that Rv2611c is the acyltransferase that catalyzes the acylation of the 6-position of the mannose residue linked to position 2 of myo-inositol in phosphatidylinositol mono- and di-mannosides, with the mono- mannosylated lipid acceptor being the primary substrate of the enzyme. We also provide the first evidence that two distinct pathways lead to the formation of acylated PIM2 from PIM1 in mycobacteria.