Steeghs L, de Cock H, Evers E, Zomer B, Tommassen J, van der Ley P
Laboratory of Vaccine Research, National Institute of Public Health and the Environment, RIVM, Antonie van Leeuwenhoeklaan 9, PO Box 1, 3720 BA Bilthoven, The Netherlands.
EMBO J. 2001 Dec 17;20(24):6937-45. doi: 10.1093/emboj/20.24.6937.
In the pathogen Neisseria meningitidis, a completely lipopolysaccharide (LPS)-deficient but viable mutant can be obtained by insertional inactivation of the lpxA gene, encoding UDP-GlcNAc acyltransferase required for the first step of lipid A biosynthesis. To study how outer membrane structure and biogenesis are affected by the absence of this normally major component, inner and outer membranes were separated and their composition analysed. The expression and assembly of integral outer membrane proteins appeared largely unaffected. However, the expression of iron limitation-inducible, cell surface-exposed lipoproteins was greatly reduced. Major changes were seen in the phospholipid composition, with a shift towards phosphatidylethanolamine and phosphatidylglycerol species containing mostly shorter chain, saturated fatty acids, one of which was unique to the LPS-deficient outer membrane. The presence of the capsular polysaccharide turned out to be essential for viability without LPS, as demonstrated by using a strain in which LPS biosynthesis could be switched on or off through a tac promoter-controlled lpxA gene. Taken together, these results can help to explain why meningococci have the unique ability to survive without LPS.
在病原菌脑膜炎奈瑟菌中，通过对lpxA基因进行插入失活可获得一种完全缺乏脂多糖（LPS）但仍具活力的突变体，lpxA基因编码脂多糖A生物合成第一步所需的UDP-葡萄糖胺酰基转移酶。为研究缺少这种通常为主要成分的物质时外膜结构和生物发生如何受到影响，对内膜和外膜进行了分离并分析其组成。外膜整合蛋白的表达和组装在很大程度上未受影响。然而，铁限制诱导的、细胞表面暴露的脂蛋白的表达大幅降低。磷脂组成出现了重大变化，向磷脂酰乙醇胺和磷脂酰甘油种类转变，这些种类大多含有较短链的饱和脂肪酸，其中一种是缺乏LPS的外膜所特有的。通过使用一种可通过tac启动子控制的lpxA基因开启或关闭LPS生物合成的菌株证明，荚膜多糖的存在对于在没有LPS的情况下的生存能力至关重要。综上所述，这些结果有助于解释为什么脑膜炎奈瑟菌具有在没有LPS的情况下生存的独特能力。
