title: Structural determination of Streptococcus pneumoniae repeat units in serotype 41A and 41F capsular polysaccharides to probe gene functions in the corresponding capsular biosynthetic loci.
abstract: We report the repeating unit structures of the native capsular polysaccharides of Streptococcus pneumoniae serotypes 41A and 41F. Structural determinations yielded six carbohydrate units in the doubly branched repeating unit to give the following structure for serotype 41A: The structure determinations were motivated (1) by an ambition to help close the remaining gaps in S. pneumoniae capsular polysaccharide structures, and (2) by the attempt to derive functional annotations of carbohydrate active enzymes in the biosynthesis of bacterial polysaccharides from the determined structures. An activity present in 41F but not 41A is identified as an acetyltransferase acting on the rhamnopyranosyl sidechain E. The genes encoding the formation of the six glycosidic bonds in serogroup 41 were determined from the capsular polysaccharide structures of serotype 41A, 41F, and genetically related serotypes, in conjunction with corresponding genomic information and computational homology searches. In combination with complementary information, NMR spectroscopy considerably simplifies the functional annotation of carbohydrate active enzymes in the biosynthesis of bacterial polysaccharides.
authors.affiliation: Novo Nordisk A/S Novo Nordisk Park, DK-2760 Måløv, Denmark.
authors.forename: Bent O
authors.initials: BO
authors.lastname: Petersen
authors.affiliation: Statens Serum Institut, Artillerivej 5, DK-2300 Copenhagen S, Denmark.
authors.forename: Ian C
authors.initials: IC
authors.lastname: Skovsted
authors.affiliation: Farmasøytisk institutt, Sem Sælands vei 3, N-0316 Oslo, Norway.
authors.forename: Berit Smestad
authors.initials: BS
authors.lastname: Paulsen
authors.affiliation: Statens Serum Institut, Artillerivej 5, DK-2300 Copenhagen S, Denmark.
authors.forename: Antonio R
authors.initials: AR
authors.lastname: Redondo
authors.affiliation: Department of Chemistry, Technical University of Denmark, Kemitorvet, Building 201, DK-2800 Kgs. Lyngby, Denmark. Electronic address: semei@kemi.dtu.dk.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Meier
mesh_terms: D000123:Acetyltransferases / Q000737:chemistry / Q000378:metabolism; D016667:Bacterial Capsules / Q000737:chemistry* / Q000235:genetics; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000235:genetics; D065288:Serogroup; D013296:Streptococcus pneumoniae / Q000737:chemistry* / Q000235:genetics / Q000472:pathogenicity
chemical_list: D011135:Polysaccharides, Bacterial; D000123:Acetyltransferases
keywords: Biosynthetic loci; Capsular polysaccharide; NMR; Serotype 41A; Streptococcus pneumoniae