title: Structure of repeating unit of the capsular polysaccharide from Acinetobacter baumannii D78 and assignment of the K4 gene cluster.
abstract: The structure of the K4 capsular polysaccharide (CPS) from a multiply antibiotic resistant Acinetobacter baumannii isolate D78 was elucidated by chemical and spectroscopical analysis. The K4 repeating unit is composed entirely by aminosugars and the trisaccharide repeating unit of the backbone polysaccharide is branched with a terminal N-acetyl-galactosamine capped with pyruvate as cyclic acetal. Each residue is in the pyranose form, α configured at the anomeric center, and has the D absolute configuration. The genes responsible for the synthesis of the K4 repeat unit and its polymerization and export are found in the capsule locus KL4 present in D78. The pyruvate acetal addition to galactosamine is formed by Ptr1, a novel pyruvate transferase, encoded at this locus.
authors: School of Molecular Bioscience, University of Sydney, Australia; Institute of Health and Biomedical Innovation, Queensland University of Technology, Australia.
authors: Johanna J
authors: JJ
authors: Kenyon
authors: Department of Chemical Sciences, University of Napoli, Italy.
authors: Immacolata
authors: I
authors: Speciale
authors: School of Molecular Bioscience, University of Sydney, Australia.
authors: Ruth M
authors: RM
authors: Hall
authors: Department of Agricultural Sciences, University of Napoli, Italy. Electronic address: decastro@unina.it.
authors: Cristina
authors: C
authors: De Castro
mesh_terms: D040981:Acinetobacter baumannii / Q000737:chemistry*; D000606:Amino Sugars / Q000737:chemistry; D016667:Bacterial Capsules / Q000737:chemistry* / Q000235:genetics*; D005798:Genes, Bacterial; D015394:Molecular Structure; D005810:Multigene Family; D014312:Trisaccharides / Q000737:chemistry
chemical_list: D000606:Amino Sugars; D014312:Trisaccharides; C063323:capsular polysaccharide K4
keywords: Acinetobacter baumannii; CPS; NMR; Pyruvate acetal; Pyruvate transferase; Structure