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K87 capsular polysaccharide (CPS) was isolated from Acinetobacter baumannii isolate LUH5547 that carries the KL87 capsule biosynthesis gene cluster at the chromosomal K locus. Studies by sugar analysis, selective chemical cleavages, and 1D and 2D 1H and 13C NMR spectroscopy showed that the CPS has a branched heptasaccharide repeat (K unit) containing one residue each of d-glucose (d-Glсp), d-glucuronic acid (d-GlсpA), N-acetyl-d-glucosamine (d-GlсpNAc), 6-deoxy-l-talose (l-6dTalp), and three residues of l-rhamnose (l-Rhap). The following structure of the CPS was established: →3)-α-L-Rhap-(1→2)-α-L-Rhap-(1→3)-α-L-6dTalp-(1→3)-β-D-GlcpNAc-(1→2↑1β-D-GlcpA-(4←1)-α-D-Glcp(2←1)-α-L-Rhap The position of a minor O-acetyl group present in the CPS was not determined. Functions of enzymes coded by genes in the KL87 gene cluster were tentatively assigned and found to be consistent with the CPS structure.

biosynthesis, structure, capsular, polysaccharide, capsular polysaccharide, group, Acinetobacter, Acinetobacter baumannii, 6-deoxy-L-talose, K locus, K87

NCBI PubMed ID: 34555685
Publication DOI: 10.1016/j.carres.2021.108439
Journal NLM ID: 0043535
Publisher: Elsevier
Correspondence: johanna.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, School of Life and Environmental Sciences, The University of Sydney, Sydney, Australia, Centre for Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology. Brisbane, Australia
Methods: 13C NMR, 1H NMR, NMR-2D, partial acid hydrolysis, sugar analysis, GLC, Smith degradation, de-O-acetylation, HPLC, GPC, bioinformatic analysis

KL55, KL74, and KL85 capsular polysaccharide (CPS) biosynthesis loci in Acinetobacter baumannii BAL_204, BAL_309, and LUH5543 genomes, respectively, are related and each contains genes for l-Rhap and d-GlcpA synthesis. The CPSs were isolated and studied by sugar analysis, Smith degradation, and 1H and 13C NMR spectroscopy. The K55 and K74 CPSs are built up of branched octasaccharide repeats (K units) containing one residue each of d-GlcpA and d-GlcpNAc and six residues of l-Rhap. The K55 unit differs from the K74 unit in the linkage between D-GlcpA and an l-Rhap residue in the K unit (1→3 versus 1→2) and linkage between K units. However, most K units in the isolated K74 CPS were modified by β-elimination of a side-chain α-l-Rhap-(1→3)-α-l-Rhap disaccharide from position 4 of GlcA to give 4-deoxy-l-threo-hex-4-enuronic acid (1:~3 ratio of intact and modified units). The K85 CPS has a branched heptasaccharide K unit similar to the K74 unit but with one fewer α-l-Rhap residue in the side chain. In contrast to previous findings on A. baumannii CPSs, each K locus includes fewer glycosyltransferase (Gtr) genes than the number required to form all linkages in the K units. Hence, one Gtr appears to be multifunctional catalysing formation of two 1→2 and one 1→3 linkages between the l-Rha residues.

Acinetobacter baumannii, capsular polysaccharide structure, β-elimination, capsule biosynthesis, rhamnosyltransferase, K locus

NCBI PubMed ID: 33159946
Publication DOI: 10.1016/j.ijbiomac.2020.11.005
Journal NLM ID: 7909578
Publisher: Butterworth-Heinemann
Correspondence: johanna.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, School of Life and Environmental Sciences, The University of Sydney, Sydney, Australia, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Australia, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, PR China
Methods: 13C NMR, 1H NMR, NMR-2D, sugar analysis, GLC, anion-exchange chromatography, mild acid hydrolysis, Smith degradation, HPLC, GPC, bioinformatic analysis, HR-ESI-MS

Whole genome sequence from Acinetobacter baumannii isolate Ab-46-1632 reveals a novel KL144 capsular polysaccharide (CPS) biosynthesis gene cluster, which carries genes for d-glucuronic acid (D-GlcA) and l-rhamnose (l-Rha) synthesis. The CPS was extracted from Ab-46-1632 and studied by 1H and 13C NMR spectroscopy, including a two-dimensional 1H,13C HMBC experiment and Smith degradation. The CPS was found to have a hexasaccharide repeat unit composed of four l-Rhap residues and one residue each of d-GlcpA and N-acetyl-d-glucosamine (D-GlcpNAc) consistent with sugar synthesis genes present in KL144. The K144 CPS structure was established and found to be related to those of A. baumannii K55, K74, K85, and K86. A comparison of the corresponding gene clusters to KL144 revealed a number of shared glycosyltransferase genes correlating to shared glycosidic linkages in the structures. One from the enzymes, encoded by only KL144 and KL86, is proposed to be a novel multifunctional rhamnosyltransfaerase likely responsible for synthesis of a shared α-l-Rhap-(1→2)-α-L-Rhap-(1→3)-L-Rhap trisaccharide fragment in the K144 and K86 structures.

capsular polysaccharide, Acinetobacter baumannii, K locus, K144, K86, multifunctional glycosyltransferase

NCBI PubMed ID: 34757131
Publication DOI: 10.1016/j.ijbiomac.2021.10.178
Journal NLM ID: 7909578
Publisher: Butterworth-Heinemann
Correspondence: asyashpirt@gmail.com
Institutions: Central Scientific Research Institute of Epidemiology, Moscow, Russia, Centre for Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology. Brisbane, Australia, D.I. Mendeleev University of Chemical Technology of Russia, Moscow, Russia, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Science, Moscow, Russia, M.M. Shemyakin and Y.A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Science, Moscow, Russia, State Research Center for Applied Microbiology and Biotechnology, Obolensk, Moscow, Region, Russia
Methods: 13C NMR, 1H NMR, NMR-2D, sugar analysis, acid hydrolysis, GLC, Smith degradation, GPC, bioinformatic analysis, HR-ESI-MS, sequencing