The capsular polysaccharide of Bacteroides fragilis comprises two ionically linked polysaccharides.
The capsular polysaccharide of Bacteroides fragilis comprises two ionically linked polysaccharides.
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DOI：
10.1016/s0021-9258(19)37177-7
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发表时间：
1992-09
期刊：
影响因子：
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通讯作者：
A. Tzianabos;Annalisa Pantosti;Herbert Baumann;J. Brisson;H J Jennings;D. L. Kasper
中科院分区：
文献类型：
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作者：
A. Tzianabos;Annalisa Pantosti;Herbert Baumann;J. Brisson;H J Jennings;D. L. Kasper
最近，我们发现脆弱拟杆菌NCTC 9343的荚膜多糖是由两个离散的大分子量多糖（称为多糖A和多糖B）的集合体组成的。通过非常温和的酸处理分解这种荚膜复合物后，高分辨率核磁共振波谱显示多糖A和B由高电荷重复单元结构和不寻常的取代基组成（Baumann， H., Tzianabos， A. O., Brisson， J.-R.）。（1992）生物化学31(1):1-4。目前，我们报道了脆弱芽孢杆菌的荚膜多糖是由多糖a和B之间的离子相互作用形成的复杂结构。免疫金标记的生物体（含多糖a和B的特异性单克隆抗体）的电镜观察表明，这两种多糖在脆弱芽孢杆菌的细胞表面共表达。我们已经证明，纯化的胶囊复合物完全由多糖A和多糖B（没有检测到其他大分子结构）以1:3.3的比例组成，并且可以通过制备等电聚焦将该复合物分解成组成多糖的天然形式。对天然多糖A和B的结构分析表明，它们与各自的酸源多糖具有相同的重复单元结构。多糖A和B之间的键的离子性质被证明是由天然多糖重新结合形成一个聚集的聚合物，与原来的配合物相当。这种大分子的独特组成可能为与脆弱芽孢杆菌荚膜多糖相关的不同寻常的生物学特性提供了基本原理。
Recently, we have shown that the capsular polysaccharide of Bacteroides fragilis NCTC 9343 is composed of an aggregate of two discrete large molecular weight polysaccharides (designated polysaccharides A and B). Following disaggregation of this capsular complex by very mild acid treatment, high resolution NMR spectroscopy demonstrated that polysaccharides A and B consist of highly charged repeating unit structures with unusual substituent groups (Baumann, H., Tzianabos, A. O., Brisson, J.-R., Kasper, D.L., and Jennings, H.J. (1992) Biochemistry 31, 4081-4089). Presently, we report that the capsular polysaccharide of B. fragilis represents a complex structure that is formed as a result of ionic interactions between polysaccharides A and B. Electron microscopy of immunogold-labeled organisms (with monoclonal antibodies specific for polysaccharides A and B) demonstrated that the two polysaccharides are co-expressed on the cell surface of B. fragilis. We have shown that the purified capsule complex is made up exclusively of polysaccharide A and polysaccharide B (no other macromolecular structure was detected) in a 1:3.3 ratio and that disaggregation of this complex into the native forms of the constituent polysaccharides could be accomplished by preparative isoelectric focusing. Structural analyses of the native polysaccharides A and B showed that they possessed the same repeating unit structures as the respective acid-derived polysaccharides. The ionic nature of the linkage between polysaccharides A and B was demonstrated by reassociation of the native polysaccharides to form an aggregated polymer comparable to the original complex. The distinctive composition of this macromolecule may provide a rationale for the unusual biologic properties associated with the B. fragilis capsular polysaccharide.