title: A membrane-located glycosyltransferase complex required for biosynthesis of the D-galactan I lipopolysaccharide O antigen in Klebsiella pneumoniae.
abstract: D-galactan I is a polysaccharide with the disaccharide repeat unit structure [-->3-beta-D-Galf-(1-->3)-alpha-D-Galp-(1-->]. This glycan represents the lipopolysaccharide O antigen found in many Gram-negative bacteria, including several Klebsiella pneumoniae O serotypes. The polysaccharide is synthesized in the cytoplasm prior to its export via an ATP-binding cassette transporter. Sequence analysis predicts three galactosyltransferases in the D-galactan I genetic locus. They are WbbO (belonging to glycosyltransferase (GT) family 4), WbbM (GT-family 8), and WbbN (GT-family 2). The WbbO and WbbM proteins are each predicted to contain two domains, with the GT modules located toward their C termini. The N-terminal domains of WbbO and WbbM exhibit no similarity to proteins with known function. In vivo complementation assays suggest that all three glycosyltransferases are required for D-galactan I biosynthesis. Using a bacterial two-hybrid system and confirmatory co-purification strategies, evidence is provided for protein-protein interactions among the glycosyltransferases, creating a membrane-located enzyme complex dedicated to d-galactan I biosynthesis.
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Veronica
authors.initials: V
authors.lastname: Kos
authors.forename: Chris
authors.initials: C
authors.lastname: Whitfield
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000737:chemistry; D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000378:metabolism; D005685:Galactans / Q000737:chemistry*; D007711:Klebsiella pneumoniae / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000737:chemistry; D008969:Molecular Sequence Data; D019081:O Antigens / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D011134:Polysaccharides / Q000737:chemistry; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017422:Sequence Analysis, DNA; D013347:Subcellular Fractions / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D018528:ATP-Binding Cassette Transporters; D005685:Galactans; D008070:Lipopolysaccharides; D019081:O Antigens; D011108:Polymers; D011134:Polysaccharides
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