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, alpha 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.
NMR, structure, Acinetobacter baumannii, pyruvate acetal, CPS, Pyruvate transferase
NCBI PubMed ID: 27509201Publication DOI: 10.1016/j.carres.2016.07.016Journal NLM ID: 0043535Publisher: Elsevier
Correspondence: C. De Castro
Institutions: School of Molecular Bioscience, University of Sydney, Australia, Institute of Health and Biomedical Innovation, Queensland University of Technology, Australia, Department of Chemical Sciences, University of Napoli, Italy, Department of Agricultural Sciences, University of Napoli, Italy
Methods: 13C NMR, 1H NMR, methylation, NMR-2D, GC-MS, sugar analysis, acid hydrolysis, mild acid hydrolysis, NMR-1D, peracetylation, SEC
Found