Leps B, Barnickel G, Bradaczek H
J Theor Biol. 1984 Mar 7;107(1):85-114. doi: 10.1016/s0022-5193(84)80123-x.
Conformational energy calculations have been used to explore the conformations which may be realized for the sugar moiety of murein and pseudomurein. For the building blocks of the pseudomurein sugar strands, i.e. for the monosaccharides beta-D-N-acetylglucosamine (NAG) and alpha-L-N-acetyltalosaminuronic acid (NAT), both in C1 ring conformation, as well as for their 1,3 and 1,4 linked disaccharides, the favoured conformations were obtained. The helical parameters of sugar strands of both linkage types, which describe the regular structure of the corresponding polysaccharides, poly-(1,3-NAT-NAG) and poly-(1,4-NAT-NAG), were calculated. Both types of polysaccharides poly-(NAG-NAT) considered in this study favoured extended conformations, which in the case of 1,3 linked polymers showed less gain of length per saccharide unit compared to 1,4 linked poly-(NAG-NAT) residues. For a 1,3 linked sugar moiety of pseudomurein every pair of neighbouring peptides attached to glycan chain pointed in favoured conformations approximately to opposite sides of the strands, whereas in a 1,4 linked poly-(NAG-NAT) the peptides protruded approximately to the same side of the glycan moiety. A comparison between pseudomurein and murein revealed that the sugar moieties of both peptidoglycans have similar features in respect to their overall structure, i.e. both favoured more or less extended structures. In contrast to these data the shapes of the resulting polysaccharide moieties were remarkably different. In poly-(1,3-NAG-NAT) the glycan chains possessed a zig-zag-like arrangement, whereas for glycan chains of the murein type relatively flat structures were preferred. These remaining differences in the conformational arrangement between both peptidoglycans depend strongly on the C1 chair conformation of NAT. It is, therefore, attractive to speculate about an hypothetical pseudomurein sugar chain configuration comprising beta-L-N-acetyltalosaminuronic acid in its 1C conformation.
构象能量计算已被用于探索胞壁质和假胞壁质糖部分可能实现的构象。对于假胞壁质糖链的构建单元，即处于C1环构象的单糖β-D-N-乙酰葡糖胺（NAG）和α-L-N-乙酰塔罗糖胺糖醛酸（NAT），以及它们的1,3和1,4连接的二糖，获得了其优势构象。计算了两种连接类型的糖链的螺旋参数，这些参数描述了相应多糖聚（1,3-NAT-NAG）和聚（1,4-NAT-NAG）的规则结构。本研究中考虑的两种类型的聚（NAG-NAT）多糖都倾向于伸展构象，其中对于1,3连接的聚合物，与1,4连接的聚（NAG-NAT）残基相比，每个糖单元的长度增加较少。对于假胞壁质的1,3连接糖部分，连接到聚糖链上的每对相邻肽以优势构象大致指向链的相对两侧，而在1,4连接的聚（NAG-NAT）中，肽大致突出到聚糖部分的同一侧。假胞壁质和胞壁质之间的比较表明，两种肽聚糖的糖部分在整体结构方面具有相似的特征，即两者都或多或少倾向于伸展结构。与这些数据相反，所得多糖部分的形状明显不同。在聚（1,3-NAG-NAT）中，聚糖链具有之字形排列，而对于胞壁质类型的聚糖链，相对扁平的结构是优选的。两种肽聚糖在构象排列上的这些剩余差异强烈取决于NAT的C1椅式构象。因此，推测一种包含处于1C构象的β-L-N-乙酰塔罗糖胺糖醛酸的假设性假胞壁质糖链构型是很有吸引力的。
