O-acetylation is a common modification of bacterial glycoconjugates. By modifying oligosaccharide structure and chemistry, O-acetylation has important consequences for biotic and abiotic recognition events and thus bacterial fitness in general. Previous studies of the broad-spectrum O-linked protein glycosylation in pathogenic Neisseria species (including N. gonorrhoeae and N. meningitidis) have revealed O-acetylation of some of their diverse glycoforms and identified the committed acetylase, PglI. Herein, we extend these observations by using mass spectrometry to examine a complete set of all glycan variants identified to date. Regardless of composition, all glycoforms and all sugars in the oligosaccharide are subject to acetylation in a PglI-dependent fashion with the only exception of di-N-acetyl-bacillosamine. Moreover, multiple sugars in a single oligosaccharide could be simultaneously modified. Interestingly, O-acetylation status was found to be correlated with altered chain lengths of oligosaccharides expressed in otherwise isogenic backgrounds. Models for how this unprecedented phenomenon might arise are discussed with some having potentially important implications for the membrane topology of glycan O-acetylation. Together, the findings provide better insight into how O-acetylation can both directly and indirectly govern glycoform structure and diversity.

中文翻译：

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细菌蛋白糖基化系统中聚糖O-乙酰化的结构和遗传分析：对聚糖链长的差异影响的证据

O-乙酰化是细菌糖缀合物的常见修饰。通过修饰寡糖的结构和化学性质，O-乙酰化对生物和非生物识别事件以及细菌的总体适应性都具有重要的意义。先前对致病性奈瑟氏菌属物种（包括淋病奈瑟氏球菌和脑膜炎奈瑟氏球菌）的广谱O联蛋白糖基化研究表明，O-乙酰化了他们各种糖型中的某些糖基，并确定了定型的乙酰化酶PglI。在本文中，我们通过使用质谱法检查迄今确定的所有聚糖变体的完整集合来扩展这些观察结果。不管组成如何，寡糖中的所有糖型和所有糖都以PglI依赖的方式进行乙酰化，唯一的例外是二-N-乙酰基细菌素。而且，单个寡糖中的多个糖可以同时被修饰。有趣的是，O发现乙酰化状态与在其他同基因背景中表达的寡糖链长的改变有关。讨论了如何出现这种前所未有的现象的模型，其中一些模型对聚糖O-乙酰化的膜拓扑具有潜在的重要意义。总之，这些发现提供了关于O-乙酰化如何直接和间接控制糖型结构和多样性的更好的见解。