The solution structure of mucous glycoproteins: proton NMR studies of native and modified ovine submaxillary mucin.
The solution structure of mucous glycoproteins: proton NMR studies of native and modified ovine submaxillary mucin.
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粘液糖蛋白的溶液结构：天然和改良绵羊颌下粘蛋白的质子核磁共振研究。
DOI：
10.1016/0003-9861(86)90581-3
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发表时间：
1986
影响因子：
3.9
通讯作者：
Gerken,TA
中科院分区：
文献类型：
--
作者：
Gerken,TA
采用质子核磁共振波谱法研究了天然和系统修饰的羊颌下黏液蛋白（OSM）的溶液结构。光谱中的大部分共振暂时归属于肽和o键双糖α- n -乙酰神经氨酸2→6 α- n -乙酰半乳糖胺质子。根据观察到的化学位移、光谱分辨率和可交换质子的行为，得出粘蛋白具有内部片段柔韧性，并以随机卷曲肽的形式存在于溶液中。没有检测到长寿命的残基间肽或碳水化合物氢键。去除(i)唾液酸残基的C8和C9碳，（ii）整个唾液酸残基，以及（iii）完整的双糖侧链，肽核构象没有显著变化。对天然黏蛋白和改性黏蛋白中的苏氨酸糖肽侧链得到了有限的质子自旋耦合常数和核超hauser增强。结果与先前报道的低聚糖中的（1→6）键和糖肽中的苏氨酸糖苷键的构象一致。OSM双糖可能以GalNAc C5C6键的扩展线性结构存在，而苏氨酸糖苷键似乎受到空间约束，尽管苏氨酸Cβo γ键可能存在多种构象。在去除末端唾液酸残基后，在糖基化苏氨酸甲基质子和GalNAc碳中检测到的小化学位移扰动与该模型一致。
The solution structure of native and systematically modified ovine submaxillary mucin (OSM) has been probed by proton NMR spectroscopic methods. Most of the resonances in the spectra have been tentatively assigned to the peptide and O-linked disaccharide, α-N-acetylneuraminic acid 2 → 6 α-N-acetylgalactosamine protons. On the basis of the observed chemical shifts, spectral resolution, and behavior of the exchangeable protons it is concluded the mucin possesses internal segmental flexibility and exists in solution as a random coil peptide. No long-lived interresidue peptide or carbohydrate hydrogen bonds were detected. The removal of (i) the C8 and C9 carbons of the sialic acid residue, (ii) the entire sialic acid residue, and (iii) the complete disaccharide side chain resulted in no significant changes in peptide core conformation. A limited set of proton spin coupling constants and nuclear Overhauser enhancements has been obtained for the threonine glycopeptide side chains in native and modified mucin. The results are consistent with the previously reported conformations for the (1 → 6) linkage in oligosaccharides and the threonyl glycosidic linkage in glycopeptides. The OSM disaccharide may exist as a extended linear structure with rotational freedom about the GalNAc C5C6 bond, while the threonine glycosidic linkage appears to be sterically constrained, although multiple conformations about the threonine CβOγbond may be allowed. The small chemical shift perturbations detected in the glycosylated threonine methyl protons and the GalNAc carbons upon removal of the terminal sialic acid residue are consistent with this model.