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A new capsular polysaccharide (CPS) biosynthesis gene cluster, KL16, was found in the genome sequence of a clinical Acinetobacter baumannii ST25 isolate, D4. The variable part of KL16 contains a module of genes for synthesis of 5,7-diacetamido-3,5,7,9-tetradeoxy-l-glycero-l-manno-non-2-ulosonic acid (5,7-di-N-acetylpseudaminic acid, Pse5Ac7Ac), a gene encoding ItrA3 that initiates the CPS synthesis with d-GlcpNAc, and two glycosyltransferase (Gtr) genes. The K16 CPS was studied by sugar analysis and Smith degradation along with 1D and 2D 1H and 13C NMR spectroscopy, and shown to be built up of linear trisaccharide repeats containing d-galactose (d-Gal), N-acetyl-d-glucosamine (d-GlcNAc), and Pse5Ac7Ac. The d-Galp residue is linked to the d-GlcpNAc initiating sugar via a β-(1→3) linkage evidently formed by a Gtr5 variant, Gtr5K16, encoded in KL16. This reveals an altered or relaxed substrate specificity of this variant as the majority of Gtr5-type glycosyltransferases have previously been shown to form a β-d-Galp-(1→3)-d-GalpNAc linkage. The β-Psep5Ac7Ac-(2→4)-d-Galp linkage is predicted to be formed by the other glycosyltransferase, Gtr37, which does not match members of any known glycosyltransferase family.

Acinetobacter baumannii, capsular polysaccharide, 5, glycosyltransferase, 7-Di-N-acetylpseudaminic acid, KL16 K locus

NCBI PubMed ID: 30664967
Publication DOI: 10.1016/j.ijbiomac.2019.01.080
Journal NLM ID: 7909578
Publisher: Butterworth-Heinemann
Correspondence: J.J. Kenyon qut.edu.au>
Institutions: N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia, M. M. Shemyakin & Y. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia, State Research Center for Applied Microbiology and Biotechnology, Obolensk, Moscow Region, Russia, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Australia, School of Life and Environmental Sciences, The University of Sydney, Sydney, Australia, Institute of Antimicrobial Chemotherapy, Smolensk State Medical University, Smolensk, Russia
Methods: 13C NMR, 1H NMR, NMR-2D, sugar analysis, GLC, Smith degradation, function analysis of gene clusters