Analyzing the functions of large glycoconjugates through the dissipative properties of their absorbed layers using the gel-forming mucin MUC5B as an example
Analyzing the functions of large glycoconjugates through the dissipative properties of their absorbed layers using the gel-forming mucin MUC5B as an example
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DOI：
10.1093/glycob/cwn024
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发表时间：
2008-06-01
期刊：
影响因子：
4.3
通讯作者：
Sheehan, John K.
中科院分区：
文献类型：
--
作者：
Kesimer, Mehmet;Sheehan, John K.
粘蛋白、蛋白聚糖和多糖等糖缀合物构成了保护细胞表层的结构基础。特别是凝胶形成的粘蛋白在上皮细胞层和环境之间定义了一个区域。这些分子的极端分子量为5-100 x 10(6)，尺寸为20-300纳米。因此，它们的生物化学与它们的物理生物化学是分不开的。结合激光散射和石英晶体质量平衡耗散法（QCM-D）研究了MUC5B粘蛋白及其同源片段在疏水表面结合时的性质。MUC5B构成了凝胶的基础，负责保护口腔、肺和颈椎管表面。通过分析疏水、金和聚苯乙烯表面与完整MUC5B分子、其还原亚基和糖基化色氨酸片段（还原后获得）的耗散相互作用，我们发现形成了40至100纳米厚的高结构水合界面。这些界面的几何形状和耗散特性主要由带负电荷的富含碳水化合物的分子结构域控制，裸露的蛋白质结构域负责附着。这些富含碳水化合物的表面具有明确的吸收特性，并允许白蛋白包覆的微珠进入和包裹在60纳米以下的吸收层。然而，大于100纳米的珠子完全被排除在表面之外。这些吸收现象与黏液膜耗散的大变化有关，因此可能不仅在生物功能（如结合病毒）中很重要，而且还可以提供黏液膜附着的表面（通常是纤毛）的信息。
Glyconjugates such as mucins, proteoglycans, and polysaccharides form the structural basis of protective cell-surface layers. In particular gel-forming mucins define a zone between the epithelial cell layer and the environment. Such molecules are of extreme molecular weight 5-100 x 10(6) and size (Rg 20-300 nm). On this account their biochemistry is inseparable from their physical biochemistry. Combining laser light scattering and quartz crystal mass balance with dissipation methods (QCM-D) we have investigated the properties of the MUC5B mucin and its cognate fragments when bound to a hydrophobic surface. MUC5B forms the basis of gels responsible for the protection of the oral cavity, lung, and cervical canal surfaces. Here we show, by analyzing dissipative interactions of hydrophobic, gold, and polystyrene surfaces, with the intact MUC5B molecule, its reduced subunits, and glycosylated tryptic fragments (obtained after reduction), the formation of 40- to 100-nm-thick highly structured, hydrated interfaces. These interfaces are dominated in their geometry and dissipative properties by the negatively charged carbohydrate-rich domains of the molecule, the naked protein domains being responsible for attachment. These carbohydrate-rich surfaces have well-defined absorptive properties and permit the entry and entrapment of albumin-coated micro-beads into the absorbed layer at and below a size of 60 nm. However beads larger than 100 nm are completely excluded from the surfaces. These absorptive phenomena correlate with large changes in film dissipation and thus may not only be important in biological functions, e.g. binding viruses, but could also be informative to the surfaces (often ciliated) onto which such mucus films are attached.