PMID:15838019

Citation	Edwards, KJ, Allen, S, Gibson, BW and Campagnari, AA (2005) Characterization of a cluster of three glycosyltransferase enzymes essential for Moraxella catarrhalis lipooligosaccharide assembly. J. Bacteriol. 187:2939-47
Abstract	Moraxella catarrhalis isolates express lipooligosaccharide (LOS) molecules on their surface, which share epitopes similar to that of the Neisseria and Haemophilus species. These common LOS epitopes have been implicated in various steps of pathogenesis for the different organisms. In this study, a cluster of three LOS glycosyltransferase genes (lgt) were identified in M. catarrhalis 7169, a strain that produces a serotype B LOS. Mutants in these glycosyltransferase genes were constructed, and the resulting LOS phenotypes were consistent with varying degrees of truncation compared to wild-type LOS. The LOS structures of each lgt mutant were no longer detected by a monoclonal antibody (MAb 4G5) specific to a highly conserved terminal epitope nor by a monoclonal antibody (MAb 3F7) specific to the serotype B LOS side chain. Mass spectrometry of the LOS glycoforms assembled by two of these lgt mutants indicated that lgt1 encodes an alpha(1-2) glucosyltransferase and the lgt2 encodes a beta(1-4) galactosyltransferase. However, these structural studies could not delineate the function for lgt3. Therefore, M. catarrhalis lgt3 was introduced into a defined beta(1-4) glucosyltransferase Haemophilus ducreyi 35000glu- mutant in trans, and monoclonal antibody analysis confirmed that Lgt3 complemented the LOS defect. These data suggest that lgt3 encodes a glucosyltransferase involved in the addition of a beta(1-4)-linked glucose to the inner core. Furthermore, we conclude that this enzymatic step is essential for the assembly of the complete LOS glycoform expressed by M. catarrhalis 7169.
Links	PubMed PMC1082826 Online version:10.1128/JB.187.9.2939-2947.2005
Keywords	Antibodies, Bacterial/immunology; Antibodies, Monoclonal/immunology; Carbohydrate Sequence; Cloning, Molecular; DNA, Bacterial/chemistry; DNA, Bacterial/isolation & purification; Epitopes/immunology; Epitopes/metabolism; Galactosyltransferases/genetics; Galactosyltransferases/metabolism; Genes, Bacterial; Genetic Complementation Test; Glucosyltransferases/genetics; Glucosyltransferases/metabolism; Glycosyltransferases/genetics; Haemophilus ducreyi/genetics; Haemophilus ducreyi/metabolism; Lipopolysaccharides/biosynthesis; Lipopolysaccharides/chemistry; Lipopolysaccharides/immunology; Mass Spectrometry; Molecular Sequence Data; Moraxella (Branhamella) catarrhalis/enzymology; Moraxella (Branhamella) catarrhalis/genetics; Multigene Family; Mutation; Sequence Analysis, DNA
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
MORCA:B0EWZ9		GO:0008378: galactosyltransferase activity	ECO:0000315:		F		Figures 3. MALDI-TOF mass spec comparison of products from mutants and revertants shows truncation at galactose addition site, suspected function as a 1,4-beta-galactosyltransferase.	complete CACAO 4191
MORCA:B0EWZ9	enables	GO:0008378: galactosyltransferase activity	ECO:0000315: mutant phenotype evidence used in manual assertion		F		Seeded From UniProt	complete
MORCA:Q5DIA0		GO:0046527: glucosyltransferase activity	ECO:0000316:	UniProtKB:Q9L875	F		Figure 4. H. ducreyi 35000glu-, a mutant deficient in a specific beta (1,4) glucosyltransferase(lgtF) was rescued by complementation with M. catarrhalis 7169 lgt3. Assay utilizes a screen with MAb 1B2-1B7, which recognizes full length LOS.	complete CACAO 4186
MORCA:Q5DIA2		GO:0046527: glucosyltransferase activity	ECO:0000315:		F		Figures 2 and 3. Fig 2, mutant missing lgt1 loses activity with MAb-4G5 and MAb-3F7. Figure 3 structural analysis and comparison from MALDI-TOF mass-spec on products of mutants and revertants suggests function as a 1,2-alpha-glucosyltransferase.	complete CACAO 4187

References

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