基于超滤膜辅助的糖蛋白全O-连接糖链的富集和MALDI-TOF/TOF质谱结构解析

哺乳动物中约有50%以上的蛋白质都发生了糖基化修饰.连接在丝氨酸或苏氨酸上的O-连接糖链是常见的蛋白质糖基化修饰方式之一,其主要功能是维持与其连接的蛋白质部分的空间构象,保护其免受蛋白酶水解及覆盖某些抗原决定簇.糖链结构的解析有助于更清楚地认识糖蛋白及其功能.本研究建立了一种基于超滤膜辅助(FASP)富集细胞、血清和尿液中糖蛋白全O-连接糖链的方法,根据糖蛋白与其糖链结构之间的分子质量差异,利用10 KD超滤膜富集蛋白质样品中由β消除反应释放的全O-连接糖链,将糖链甲基化修饰后再使用MALDI-TOF/TOF-MS进行解析,同时利用二级质谱进行结构确认.通过上述方法可从标准糖蛋白mucin、细胞、血清和尿液样本中分别鉴定到83、29、33和85种O-连接糖链结构,利用该方法可以从复杂样品中富集和解析糖蛋白全O-连接糖链,实现快速、高效、高通量地解析糖蛋白O-连接糖链的目的.

Enrichment and Characterization of Total O-linked Glycans From Glycoproteins by Ultrafiltration Units and Mass Spectrometry

Approximately more than half of mammalian proteins are glycosylated. O-linked glycan, attached to protein via serine or threonine residue, is one of common post-translation modifications on proteins. Its main functions include maintaining the conformation of the protein connected, protecting it from proteolysis, and covering some antigenic determinant. Analysis of O-linked glycan structure of glycoproteins can contribute to a clearer understanding of glycoproteins and their functions. This study describes a new strategy, involving enrichment and separation of total O-glycan from the glycoproteins based on a filter assisted sample preparation method (O-glycan-FASP), which was developed using ultrafiltration units according to the molecular mass differences among the glycans and proteins. The glycans were characterized and confirmed by MALDI-TOF/TOF-MS. A total of 105, 29, 33 and 85 distinctive O-glycan were characterized from bovine submaxillary mucin (BSM), human cell, serum and urine respectively.