Paramonov Nikolay, Rangarajan Minnie, Hashim Ahmed, Gallagher Alex, Aduse-Opoku Joseph, Slaney Jennifer M, Hounsell Elizabeth, Curtis Michael A
MRC Molecular Pathogenesis Group, Centre for Infectious Disease, Institute of Cell and Molecular Science, Barts and The London, Queen Mary's School of Medicine and Dentistry, 4 Newark Street, London E1 2AT, UK.
Mol Microbiol. 2005 Nov;58(3):847-63. doi: 10.1111/j.1365-2958.2005.04871.x.
The Arg-gingipains (RgpsA and B) of Porphyromonas gingivalis are a family of extracellular cysteine proteases and are important virulence determinants of this periodontal bacterium. A monoclonal antibody, MAb1B5, which recognizes an epitope on glycosylated monomeric RgpAs also cross-reacts with a cell-surface polysaccharide of P. gingivalis W50 suggesting that the maturation pathway of the Arg-gingipains may be linked to the biosynthesis of a surface carbohydrate. We report the purification and structural characterization of the cross-reacting anionic polysaccharide (APS), which is distinct from both the lipopolysaccharide and serotype capsule polysaccharide of P. gingivalis W50. The structure of APS was determined by 1D and 2D NMR spectroscopy and methylation analysis, which showed it to be a phosphorylated branched mannan. The backbone is built up of alpha-1,6-linked mannose residues and the side-chains contain alpha-1,2-linked mannose oligosaccharides of different lengths (one to two sugar residues) attached to the backbone via 1,2-linkage. One of the side-chains in the repeating unit contains Manalpha1-2Manalpha1-phosphate linked via phosphorus to a backbone mannose at position 2. De-O-phosphorylation of APS abolished cross-reactivity suggesting that Manalpha1-2Manalpha1-phosphate fragment forms part of the epitope recognized by MAb1B5. This phosphorylated branched mannan represents a novel polysaccharide that is immunologically related to the post-translational additions of Arg-gingipains.
牙龈卟啉单胞菌的精氨酸牙龈蛋白酶（RgpsA和B）是一类细胞外半胱氨酸蛋白酶，是这种牙周细菌重要的毒力决定因素。一种单克隆抗体MAb1B5可识别糖基化单体RgpAs上的一个表位，它还与牙龈卟啉单胞菌W50的细胞表面多糖发生交叉反应，这表明精氨酸牙龈蛋白酶的成熟途径可能与一种表面碳水化合物的生物合成有关。我们报道了交叉反应性阴离子多糖（APS）的纯化及结构表征，该多糖与牙龈卟啉单胞菌W50的脂多糖和血清型荚膜多糖均不同。通过一维和二维核磁共振光谱以及甲基化分析确定了APS的结构，结果表明它是一种磷酸化的支链甘露聚糖。主链由α-1,6-连接的甘露糖残基组成，侧链包含不同长度（一至两个糖残基）的α-1,2-连接的甘露糖寡糖，它们通过1,2-连接与主链相连。重复单元中的一个侧链包含通过磷与2位主链甘露糖相连的Manα1-2Manα1-磷酸。APS的去磷酸化消除了交叉反应性，这表明Manα1-2Manα1-磷酸片段构成了MAb1B5识别的表位的一部分。这种磷酸化的支链甘露聚糖代表了一种新型多糖，它在免疫上与精氨酸牙龈蛋白酶的翻译后修饰有关。
