Proteomics of Campylobacter glycosylation

N-linked glycosylation is an essential virulence determinant in Campylobacter jejuni, the major causative agent of gastroenteritis in the developed world. Glycosylation is encoded by the pgl gene cluster which encodes for the biosynthesis and attachment of a conserved heptasaccharide glycan to proteins in the C. jejuni periplasm. Over 80 membrane-associated proteins have been identified, however the functional role played by glycan attachment is almost completely unknown. We used quantitative proteomics by label-based and targeted strategies to examine glycosylation negative C. jejuni in comparison to wild-type. These technical approaches were considered as ‘discovery’ (label-based) and ‘validation’ data sets in our subsequent analysis. Inclusion of a glycosylation restored strain enabled us to further exploit the proteomics data to exclude non-specific protein abundance changes that could be considered as off-target effects. These data have provided a reference set of changes associated with protein N-glycosylation that could subsequently be tested by phenotypic analysis to determine the role of this modification in Campylobacter biology.

N-糖基化（N-linked glycosylation）是空肠弯曲杆菌（Campylobacter jejuni）的关键毒力决定因子，而该菌是发达国家肠胃炎的主要致病菌。其糖基化过程由pgl基因簇（pgl gene cluster）编码，该基因簇负责催化保守七糖聚糖（heptasaccharide glycan）的生物合成，并将其连接至空肠弯曲杆菌周质（periplasm）内的蛋白质。目前已鉴定出超过80种膜相关蛋白（membrane-associated proteins），但聚糖修饰的具体功能仍几乎完全未知。本研究采用基于标记法与靶向策略的定量蛋白质组学（quantitative proteomics）技术，对比分析糖基化缺陷型空肠弯曲杆菌与野生型菌株的蛋白表达差异。上述两种技术方法在后续分析中分别被划分为“发现数据集”与“验证数据集”。引入糖基化恢复菌株后，我们可进一步利用蛋白质组学数据，排除可归类为脱靶效应（off-target effects）的非特异性蛋白质丰度变化。本研究所得数据构建了与蛋白质N-糖基化相关的差异表达参考数据集，后续可通过表型分析（phenotypic analysis）验证该修饰在弯曲杆菌生物学中的功能角色。