title: Biosynthesis of uronamide sugars in Pseudomonas aeruginosa O6 and Escherichia coli O121 O antigens.
abstract: The major component of the outer leaflet of the outer membrane of Gram-negative bacteria is lipopolysaccharide (LPS). The outermost domain of LPS is a polysaccharide called O antigen. Pseudomonas aeruginosa establishes biofilms on wet surfaces in a wide range of habitats and mutations in O-antigen biosynthesis genes affect bacterial adhesion and the structure of these biofilms. The P. aeruginosa O6 O antigen contains a 2-acetamido-2-deoxy-d-galacturonamide (d-GalNAcAN) residue. O-antigen biosynthesis in this serotype requires the wbpS gene, which encodes a protein with conserved domains of the glutamine-dependent amidotransferase family. Replacement of conserved amino acids in the N-terminal glutaminase conserved domain of WbpS inhibited O-antigen biosynthesis under restricted-ammonia conditions, but not in rich media; suggesting that this domain functions to provide ammonia for O-antigen biosynthesis under restricted-ammonia conditions, by hydrolysis of glutamine. Escherichia coli O121 also produces a d-GalNAcAN-containing O antigen, and possesses a homologue of wbpS called wbqG. An E. coli O121 wbqG mutant was cross-complemented by providing wbpS in trans, and vice versa, showing that these two genes are functionally interchangeable. The E. coli O121 wbqG mutant O antigen contains 2-acetamido-2-deoxy-d-galacturonate (d-GalNAcA), instead of d-GalNAcAN, demonstrating that wbqG is specifically required for biosynthesis of the carboxamide in this sugar.
authors.affiliation: Department of Molecular and Cellular Biology, University of Guelph, Ontario N1G 2W1, Canada.
authors.forename: Jerry D
authors.initials: JD
authors.lastname: King
authors.forename: Evgeny
authors.initials: E
authors.lastname: Vinogradov
authors.forename: Vanessa
authors.initials: V
authors.lastname: Tran
authors.forename: Joseph S
authors.initials: JS
authors.lastname: Lam
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D004926:Escherichia coli / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D005816:Genetic Complementation Test; D005972:Glutaminase / Q000378:metabolism; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D019081:O Antigens / Q000096:biosynthesis* / Q000737:chemistry* / Q000276:immunology; D011550:Pseudomonas aeruginosa / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D014574:Uronic Acids / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D019081:O Antigens; C110323:O-antigen, E.coli O121; D014574:Uronic Acids; D005972:Glutaminase