Truncated structural variants of lipoarabinomannan in ethambutol drug-resistant strains of Mycobacterium smegmatis - Inhibition of arabinan biosynthesis by ethambutol
Truncated structural variants of lipoarabinomannan in ethambutol drug-resistant strains of Mycobacterium smegmatis - Inhibition of arabinan biosynthesis by ethambutol
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DOI：
10.1074/jbc.271.45.28682
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发表时间：
1996-11-08
影响因子：
4.8
通讯作者：
Chatterjee, D
中科院分区：
文献类型：
--
作者：
Khoo, KH;Douglas, E;Chatterjee, D
抗结核药物乙胺丁醇（Emb）以前被证明可以抑制结核分枝杆菌和其他分枝杆菌的细胞壁阿拉伯半乳聚糖（AG）和脂阿拉伯甘露聚糖（LAM）的阿拉伯聚糖合成。然而，通过在含有递增浓度Emb的培养基中连续传代耻垢分枝杆菌亲本菌株而分离的Emb抗性突变体，当维持在10 μ g/ml Emb上时，在合成正常形式的AG的同时产生截短形式的LAM（Mikusova，K.，斯莱登河一、贝斯拉湾美国，和Brennan，P.J.（1995）Antimicrob.探员凯莫特。39，2482-2489）。我们现在已经分离并表征了由抗性突变体和用含有来自鸟分枝杆菌的编码Emb抗性的emb区域的质粒转染的重组菌株所产生的截短的LAM。通过化学分析，endoarabinanase消化，高pH阴离子交换色谱，和质谱分析，截断被证明主要是一个结果的选择性和部分抑制的线性阿拉伯聚糖末端基序的合成，这构成了很大一部分的阿拉伯聚糖末端的LAM，但不是AG。然而，在较高浓度下，Emb也影响了用于AG和LAM的阿拉伯聚糖的一般生物合成，导致严重截短的LAM以及具有降低的Ara：Gal比率的AG。结果表明，Emb发挥其抗分枝杆菌的作用，通过抑制一系列的阿拉伯糖基转移酶参与生物合成的阿拉伯聚糖独特的分枝杆菌细胞壁。进一步得出结论，AG和LAM共同的独特分支的末端Ara（6）基序是功能性细胞壁的基本结构实体，因此，负责其合成的生物合成机制是Emb作为强效抗结核药物的有效靶点。
The anti-tuberculosis drug, ethambutol (Emb), was previously shown to inhibit the synthesis of arabinans of both the cell wall arabinogalactan (AG) and lipoarabinomannan (LAM) of Mycobacterium tuberculosis and other mycobacteria. However, an Emb-resistant mutant, isolated by consecutive passage of the Mycobacterium smegmatis parent strain in media containing increasing concentrations of Emb, while synthesizing a normal version of AG, produced truncated forms of LAM when maintained on 10 mu g/ml Emb (Mikusova, K., Slayden, R. A., Besra, G. S., and Brennan, P. J. (1995) Antimicrob. Agents Chemother. 39, 2482-2489). We have now isolated and characterized the truncated LAMs made by both the resistant mutant and a recombinant strain transfected with a plasmid containing the emb region from Mycobacterium avium which encodes for Emb resistance. By chemical analysis, endoarabinanase digestion, high pH anion exchange chromatography, and mass spectrometry analyses, truncation was demonstrated as primarily a consequence of selective and partial inhibition of the synthesis of the linear arabinan terminal motif, which constitutes a substantial portion of the arabinan termini in LAM but not of AG. However, at higher concentrations, Emb also affected the general biosynthesis of arabinan destined for both AG and LAM, resulting in severely truncated LAM as well as AG with a reduced Ara:Gal ratio. The results suggested that Emb exerts its antimycobacterial effect by inhibiting an array of arabinosyltransferases involved in the biosynthesis of arabinans unique to the mycobacterial cell wall. It was further concluded that the uniquely branched terminal Ara(6) motif common to both AG and LAM is an essential structural entity for a functional cell wall and, consequently, that the biosynthetic machinery responsible for its synthesis is the effective target of Emb in its role as a potent anti-tuberculosis drug.