Conformational analysis of an extracellular polysaccharide produced by Sphaerotilus natans
Conformational analysis of an extracellular polysaccharide produced by Sphaerotilus natans
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DOI：
10.1016/j.carres.2012.07.023
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发表时间：
2012-10-01
影响因子：
3.1
通讯作者：
Ueda, Kazuyoshi
中科院分区：
文献类型：
--
作者：
Kondo, Keiko;Takeda, Minoru;Ueda, Kazuyoshi
浮游球衣菌是一种丝状菌鞘形成菌，常见于膨胀的活性污泥中。这种细菌的庞大性质是由胞外多糖（EPS）引起的。EPS是具有以下化学结构的线性酸性多糖：[-> 4）-a-D-Glcp-（1 -> 2）-β-D-GlcpA-（1 -> 2）-a-L-Rhap-（1 -> 3）-β-L-Rhap-（1（->）]（n）。通过H-1-H-1和H-1-C-13相关核磁共振（NMR）实验获得核Overhauser效应信号，用于构象解析。对EPS结构单元的每个二糖单元进行分子力学计算。在计算结果的基础上，估计了五糖片段的构象。在确认NMR数据和五糖片段的预测构象之间的一致性之后，使用相同的程序估计十七糖片段的构象。十七糖形成（12/1）螺旋并局部折叠链，这归因于一系列残基α-D-Glcp-（1 -> 2）-β-D-GlcpA-（1-> 2）-α-L-Rhap形成的三角形排列。这种排列是由特殊的连续（1 -> 2）键引起的，并由α-葡糖基和α-鼠李糖基残基之间的氢键加强。考虑到由于这种三角形排列的空间位阻，EPS分子不应该在水性环境中形成双螺旋。我们建议将EPS的这种独特的化学结构和性质命名为“球形”。(C)2012爱思唯尔有限公司版权所有。
Sphaerotilus natans is a filamentous sheath-forming bacterium, commonly found in bulking activated sludge. The bulky nature of this bacterium is caused by an extracellular polysaccharide (EPS). EPS is a linear acidic polysaccharide with the following chemical structure: [-> 4)-alpha-D-Glcp-(1 -> 2)-beta-D-GlcpA- (1 -> 2)-alpha-L-Rhap-(1 -> 3)-beta-L-Rhap-(1(->)](n). H-1-H-1 and H-1-C-13 correlation nuclear magnetic resonance (NMR) experiments were performed to acquire nuclear Overhauser effect signals, which were used for conformational elucidation. Molecular mechanics calculations were performed on each disaccharide unit of the EPS building blocks. On the basis of the results of the calculations, the conformation of a pentasaccharide fragment was estimated. After confirmation of the coincidence between the NMR data and the predicted conformation of the pentasaccharide fragment, the conformation of a heptadecasaccharide fragment was estimated using the same procedure. The heptadecasaccharide was found to form a (12/1) helix and take locally folded chain, which is attributed to a triangular arrangement formed by a series of residues, alpha-D-Glcp-(1 -> 2)-beta-D-GlcpA-(1 -> 2)-alpha-L-Rhap. This arrangement is caused by the peculiar consecutive (1 -> 2) linkages and reinforced by a hydrogen bond between the alpha-glucosyl and alpha-rhamnosyl residues. Considering the steric hindrance due to this triangular arrangement, EPS molecules are not supposed to form double helix in an aqueous environment. We propose the name 'sphaeran' to refer to this unique chemical structure and properties of EPS. (C) 2012 Elsevier Ltd. All rights reserved.