Complete chemical structure of the K135 capsular polysaccharide produced by Acinetobacter baumannii RES-546 that contains 5,7-di-N-acetyl-8-epipseudaminic acid

• Published in: Carbohydrate research 2023-01, Vol.523, p.108726-108726, Article 108726
• Main Authors: Shashkov, Alexander S., Kasimova, Anastasiya A., Arbatsky, Nikolay P., Senchenkova, Sof'ya N., Perepelov, Andrei V., Dmitrenok, Andrei S., Chizhov, Alexander O., Knirel, Yuriy A., Shneider, Mikhail M., Popova, Anastasia V., Kenyon, Johanna J.
• Format: Article
• Language: English
• Subjects: 5,7-Diacetamido-3,5,7,9-tetradeoxynon-2-ulosonic acid; Acinetobacter baumannii; Acinetobacter baumannii - chemistry; Bacterial Capsules - chemistry; Capsular polysaccharide; Glycosyltransferases - genetics; K135; Multigene Family; Polysaccharides - analysis; Polysaccharides, Bacterial - chemistry; Sugars
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/j.carres.2022.108726

A structurally diverse capsular polysaccharide (CPS) in the outer cell envelope plays an important role in the virulence of the important bacterial pathogen, Acinetobacter baumannii. More than 75 different CPS structures have been determined for the species to date, and many CPSs include isomers of a higher sugar, namely 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acid. Recently, a novel isomer having the d-glycero-l-manno configuration (5,7-di-N-acetyl-8-epipseudaminic acid; 8ePse5Ac7Ac) has been identified in the CPS from A. baumannii clinical isolate RES-546 [Carbohydr. Res. 513 (2022) 108,531]. Here, the complete chemical structure of this CPS, designated K135, was elucidated. The CPS was found to have a branched tetrasaccharide K unit and to include the higher sugar as part of a 8ePse5Ac7Ac-(2 → 6)-α-Gal disaccharide branching from a →3)-α-D-GlcpNAc-(1 → 3)-β-D-GlcpNAc-(1→ main chain. Assignment of glycosyltransferases encoded by the CPS biosynthesis gene cluster in the RES-546 genome enabled the first sugar of the K unit, and hence the topology of the K135 CPS, to be determined. [Display omitted] •Complete structure of Acinetobacter baumannii K135 solved.•Annotations for the KL135 gene cluster reported.•Genes for 8Pse5Ac7Ac were not found at the K locus.