Lithgow Karen V, Scott Nichollas E, Iwashkiw Jeremy A, Thomson Euan L S, Foster Leonard J, Feldman Mario F, Dennis Jonathan J
Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada, T6G 2E9.
Mol Microbiol. 2014 Apr;92(1):116-37. doi: 10.1111/mmi.12540. Epub 2014 Mar 5.
Bacteria of the Burkholderia cepacia complex (Bcc) are pathogens of humans, plants, and animals. Burkholderia cenocepacia is one of the most common Bcc species infecting cystic fibrosis (CF) patients and its carriage is associated with poor prognosis. In this study, we characterized a general O-linked protein glycosylation system in B. cenocepacia K56-2. The PglLBc O-oligosaccharyltransferase (O-OTase), encoded by the cloned gene bcal0960, was shown to be capable of transferring a heptasaccharide from the Campylobacter jejuni N-glycosylation system to a Neisseria meningitides-derived acceptor protein in an Escherichia coli background, indicating that the enzyme has relaxed specificities for both the sugar donor and protein acceptor. In B cenocepacia K56-2, PglLBc is responsible for the glycosylation of 23 proteins involved in diverse cellular processes. Mass spectrometry analysis revealed that these proteins are modified with a trisaccharide HexNAc-HexNAc-Hex, which is unrelated to the O-antigen biosynthetic process. The glycosylation sites that were identified existed within regions of low complexity, rich in serine, alanine, and proline. Disruption of bcal0960 abolished glycosylation and resulted in reduced swimming motility and attenuated virulence towards both plant and insect model organisms. This study demonstrates the first example of post-translational modification in Bcc with implications for pathogenesis.
洋葱伯克霍尔德菌复合体（Bcc）细菌是人类、植物和动物的病原体。洋葱伯克霍尔德菌是感染囊性纤维化（CF）患者最常见的Bcc菌种之一，其携带与不良预后相关。在本研究中，我们对洋葱伯克霍尔德菌K56-2中的一种通用O-连接蛋白糖基化系统进行了表征。由克隆基因bcal0960编码的PglLBc O-寡糖基转移酶（O-OTase）被证明能够在大肠杆菌背景下将空肠弯曲菌N-糖基化系统中的七糖转移至脑膜炎奈瑟菌来源的受体蛋白，这表明该酶对糖供体和蛋白受体都具有宽松的特异性。在洋葱伯克霍尔德菌K56-2中，PglLBc负责23种参与不同细胞过程的蛋白的糖基化。质谱分析显示，这些蛋白被一种三糖HexNAc-HexNAc-Hex修饰，这与O抗原生物合成过程无关。鉴定出的糖基化位点存在于低复杂性区域内，富含丝氨酸、丙氨酸和脯氨酸。bcal0960的破坏消除了糖基化，并导致游动性降低以及对植物和昆虫模式生物的毒力减弱。本研究展示了Bcc中翻译后修饰的首个实例，对发病机制具有重要意义。
