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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Quantitative lipid composition of cell envelopes of Corynebacterium glutamicum elucidated through reverse micelle extraction
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Quantitative lipid composition of cell envelopes of Corynebacterium glutamicum elucidated through reverse micelle extraction

机译：反向胶束提取法阐明谷氨酸棒杆菌细胞膜的定量脂质组成

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摘要

Cells of the Corynebacterium-Nocardia-Mycobacterium group of bacteria are surrounded by an outer membrane (OM) containing mycolic acids that are covalently linked to the underlying arabino-galactan-peptidoglycan complex. This OM presumably acts as a permeability barrier that imparts high levels of intrinsic drug resistance to some members of this group, such as Mycobacterium tuberculosis, and its component lipids have been studied intensively in a qualitative manner over the years. However, the quantitative lipid composition of this membrane has remained obscure, mainly because of difficulties in isolating it without contamination from the inner cytoplasmic membrane. Here we use the extraction, with reverse surfactant micelles, of intact cells of Corynebacterium glutamicum and show that this method extracts the free OM lipids quantitatively with no contamination from lipids of the cytoplasmic membrane, such as phosphatidylglycerol. Although only small amounts of corynomycolate were esterified to arabinogalactan, a large amount of cardiolipin was present in a nonextractable form, tightly associated, possibly covalently, with the peptidogly-can-arabinogalactan complex. Furthermore, we show that the OM contains just enough lipid hydrocarbons to produce a bilayer covering the cell surface, with its inner leaflet composed mainly of the aforementioned nonextractable cardiolipin and its outer leaflet composed of trehalose dimycolates, phosphatidylinositol manno-sides, and highly apolar lipids, similar to the Minnikin model of 1982. The reverse micelle extraction method is also useful for extracting proteins associated with the OM, such as porins.
机译：细菌的棒状杆菌-诺卡氏菌-分枝杆菌属的细胞被外膜（OM）所包围，该膜包含共价连接至下面的阿拉伯半乳聚糖-肽聚糖复合物的分枝菌酸。这种OM可能是通透性屏障，可为该组中的某些成员（例如结核分枝杆菌）赋予高水平的内在抗药性，并且多年来已对其定性脂质进行了深入研究。然而，该膜的定量脂质组成仍然不清楚，主要是因为难以在不从内部细胞质膜污染的情况下分离该膜。在这里，我们使用反向表面活性剂胶束提取谷氨酸棒状杆菌完整细胞的方法，结果表明该方法定量提取了游离的OM脂质，而没有污染，这些杂质来自细胞质膜的脂质，例如磷脂酰甘油。尽管只有少量的胭脂红被酯化为阿拉伯半乳聚糖，但是大量的心磷脂以不可提取的形式存在，与肽聚糖-can-阿拉伯半乳聚糖复合物紧密地共价结合。此外，我们显示OM包含足够的脂质烃以产生覆盖细胞表面的双层膜，其内部小叶主要由上述不可提取的心磷脂组成，其外部小叶由海藻糖二糖酸酯，磷脂酰肌醇甘露糖苷和高度非极性脂质组成，类似于1982年的Minnikin模型。反胶束提取方法也可用于提取与OM相关的蛋白质，例如孔蛋白。

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