School of Molecular and Microbial Biosciences, University of Sydney, Sydney, Australia.
Mol Cell Proteomics. 2011 Feb;10(2):M000031-MCP201. doi: 10.1074/mcp.M000031-MCP201. Epub 2010 Apr 1.
Campylobacter jejuni is a gastrointestinal pathogen that is able to modify membrane and periplasmic proteins by the N-linked addition of a 7-residue glycan at the strict attachment motif (D/E)XNX(S/T). Strategies for a comprehensive analysis of the targets of glycosylation, however, are hampered by the resistance of the glycan-peptide bond to enzymatic digestion or β-elimination and have previously concentrated on soluble glycoproteins compatible with lectin affinity and gel-based approaches. We developed strategies for enriching C. jejuni HB93-13 glycopeptides using zwitterionic hydrophilic interaction chromatography and examined novel fragmentation, including collision-induced dissociation (CID) and higher energy collisional (C-trap) dissociation (HCD) as well as CID/electron transfer dissociation (ETD) mass spectrometry. CID/HCD enabled the identification of glycan structure and peptide backbone, allowing glycopeptide identification, whereas CID/ETD enabled the elucidation of glycosylation sites by maintaining the glycan-peptide linkage. A total of 130 glycopeptides, representing 75 glycosylation sites, were identified from LC-MS/MS using zwitterionic hydrophilic interaction chromatography coupled to CID/HCD and CID/ETD. CID/HCD provided the majority of the identifications (73 sites) compared with ETD (26 sites). We also examined soluble glycoproteins by soybean agglutinin affinity and two-dimensional electrophoresis and identified a further six glycosylation sites. This study more than doubles the number of confirmed N-linked glycosylation sites in C. jejuni and is the first to utilize HCD fragmentation for glycopeptide identification with intact glycan. We also show that hydrophobic integral membrane proteins are significant targets of glycosylation in this organism. Our data demonstrate that peptide-centric approaches coupled to novel mass spectrometric fragmentation techniques may be suitable for application to eukaryotic glycoproteins for simultaneous elucidation of glycan structures and peptide sequence.
空肠弯曲菌是一种胃肠道病原体,能够通过在严格附着基序(D/E)XNX(S/T)处添加 7 个残基聚糖,修饰膜和周质蛋白。然而,由于聚糖-肽键对酶消化或β消除的抗性,全面分析糖基化靶标的策略受到阻碍,并且以前集中于与凝集素亲和力和基于凝胶的方法兼容的可溶性糖蛋白。我们开发了使用两性离子亲水性相互作用色谱法富集空肠弯曲菌 HB93-13 糖肽的策略,并研究了新型片段化,包括碰撞诱导解离(CID)和更高能量碰撞(C-trap)解离(HCD)以及 CID/电子转移解离(ETD)质谱法。CID/HCD 能够鉴定聚糖结构和肽骨架,从而允许糖肽鉴定,而 CID/ETD 通过保持糖肽键来阐明糖基化位点。通过使用两性离子亲水性相互作用色谱法与 CID/HCD 和 CID/ETD 结合的 LC-MS/MS 鉴定了 130 种糖肽,代表 75 个糖基化位点。与 ETD(26 个位点)相比,CID/HCD 提供了大多数鉴定结果(73 个位点)。我们还通过大豆凝集素亲和和二维电泳研究了可溶性糖蛋白,并鉴定了另外六个糖基化位点。本研究使空肠弯曲菌中经证实的 N 连接糖基化位点数量增加了一倍以上,并且是首次利用 HCD 片段化用于具有完整聚糖的糖肽鉴定。我们还表明,该生物体中的疏水性整合膜蛋白是糖基化的重要靶标。我们的数据表明,与新型质谱碎裂技术相结合的基于肽的方法可能适用于真核糖蛋白,以同时阐明聚糖结构和肽序列。