Characterization of a trifunctional glucosyltransferase essential for Moraxella catarrhalis lipooligosaccharide assembly

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DOIResolve DOI: http://doi.org/10.1093/glycob/cwt042
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TypeArticle
Journal titleGlycobiology
ISSN0959-6658
Volume23
Issue8
Pages10131021; # of pages: 9
Subjectglucosyltransferase; lipooligosaccharide; amino terminal sequence; article; bacterial strain; biosynthesis; carbohydrate synthesis; carboxy terminal sequence; catalysis; Escherichia coli; Moraxella catarrhalis; nonhuman; nucleotide sequence; Pasteurella multocida; phenotype; priority journal; protein domain; protein motif; Streptococcus pyogenes
AbstractThe human respiratory tract pathogen Moraxella catarrhalis expresses lipooligosaccharides (LOS), glycolipid surface moieties that are associated with enhanced colonization and virulence. Recent studies have delineated the major steps required for the biosynthesis and assembly of the M. catarrhalis LOS molecule. We previously demonstrated that the glucosyltransferase enzyme Lgt3 is responsible for the addition of at least one glucose (Glc) molecule, at the β-(1-4) position, to the inner core of the LOS molecule. Our data further suggested a potential multifunctional role for Lgt3 in LOS biosynthesis. The studies reported here demonstrate that the Lgt3 enzyme possesses two glycosyltransferase domains (A1 and A2) similar to that of other bifunctional glycosyltransferase enzymes involved in surface polysaccharide biosynthesis in Escherichia coli, Pasteurella multocida and Streptococcus pyogenes. Each Lgt3 domain contains a conserved DXD motif, shown to be involved in the catalytic activity of other glycosyltransferases. To determine the function of each domain, A1 (N-terminal), A2 (C-terminal) and double A1A2 site-directed DAD to AAA mutants were constructed and the resulting LOS phenotypes of these modified strains were analyzed. Our studies indicate that the Lgt3 N-terminal A1 catalytic domain is responsible for the addition of the first β-(1-3) Glc to the first Glc on the inner core. The C-terminal catalytic domain A2 then adds the β-(1-4) Glc and the β-(1-6) Glc, confirming the bifunctional nature of this domain. The results from these experiments demonstrate that Lgt3 is a novel, multifunctional transferase responsible for the addition of three Glcs with differing linkages onto the inner core of M. catarrhalis LOS. © 2013 The Author 2013.
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LanguageEnglish
AffiliationNational Research Council Canada (NRC-CNRC); NRC Institute for Biological Sciences (IBS-ISB)
Peer reviewedYes
NPARC number21269757
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Record identifierf70abfce-d6e3-4d3a-8b63-900c9d4c2fe1
Record created2013-12-13
Record modified2016-05-09
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