Tropis Marielle, Meniche Xavier, Wolf Andreas, Gebhardt Henrike, Strelkov Sergey, Chami Mohamed, Schomburg Dietmar, Krämer Reinhard, Morbach Susanne, Daffé Mamadou
Department of Molecular Mechanisms of Mycobacterial Infections, Institut de Pharmacologie et Biologie Structurale (UMR 5089 du CNRS et de l'Université Paul Sabatier) 205, route de Narbonne, 31077 Toulouse cedex 04, France.
J Biol Chem. 2005 Jul 15;280(28):26573-85. doi: 10.1074/jbc.M502104200. Epub 2005 May 18.
Trehalose (alpha-D-glucopyranosyl-alpha'-D-glucopyranoside) is essential for the growth of the human pathogen Mycobacterium tuberculosis but not for the viability of the phylogenetically related corynebacteria. To determine the role of trehalose in the physiology of these bacteria, the so-called Corynebacterineae, mutant strains of Corynebacterium glutamicum unable to synthesize trehalose due to the knock-out of the genes of the three pathways of trehalose biosynthesis, were biochemically analyzed. We demonstrated that the synthesis of trehalose under standard conditions is a prerequisite for the production of mycolates, major and structurally important constituents of the cell envelope of Corynebacterineae. Consistently, the trehalose-less cells also lack the cell wall fracture plane that typifies mycolate-containing bacteria. Importantly, however, the mutants were able to synthesize mycolates when grown on glucose, maltose, and maltotriose but not on other carbon sources known to be used for the production of internal glucose phosphate such as fructose, acetate, and pyruvate. The mycoloyl residues synthesized by the mutants grown on alpha-D-glucopyranosyl-containing oligosaccharides were transferred both onto the cell wall and free sugar acceptors. A combination of chemical analytical approaches showed that the newly synthesized glycolipids consisted of 1 mol of mycolate located on carbon 6 of the non reducing glucopyranosyl unit. Additionally, experiments with radioactively labeled trehalose showed that the transfer of mycoloyl residues onto sugars occurs outside the plasma membrane. Finally, and in contradiction to published data, we demonstrated that trehalose 6-phosphate has no impact on mycolate synthesis in vivo.
海藻糖（α-D-吡喃葡萄糖基-α'-D-吡喃葡萄糖苷）对于人类病原体结核分枝杆菌的生长至关重要，但对于系统发育相关的棒状杆菌的生存能力却并非如此。为了确定海藻糖在这些细菌（即所谓的棒杆菌科）生理学中的作用，对谷氨酸棒杆菌的突变菌株进行了生化分析，这些菌株由于海藻糖生物合成的三条途径的基因敲除而无法合成海藻糖。我们证明，在标准条件下海藻糖的合成是霉菌酸产生的先决条件，霉菌酸是棒杆菌科细胞壁的主要且结构重要的成分。一致地，缺乏海藻糖的细胞也缺乏典型的含霉菌酸细菌的细胞壁断裂平面。然而，重要的是，当在葡萄糖、麦芽糖和麦芽三糖上生长时，这些突变体能够合成霉菌酸，但在已知用于产生内部葡萄糖磷酸的其他碳源（如果糖、乙酸盐和丙酮酸盐）上生长时则不能。在含α-D-吡喃葡萄糖基的寡糖上生长的突变体合成的霉菌酰残基既转移到细胞壁上，也转移到游离糖受体上。化学分析方法的组合表明，新合成的糖脂由1摩尔位于非还原吡喃葡萄糖基单元碳6上的霉菌酸组成。此外，用放射性标记的海藻糖进行的实验表明，霉菌酰残基向糖的转移发生在质膜外。最后，与已发表的数据相反，我们证明6-磷酸海藻糖在体内对霉菌酸合成没有影响。
