title: Post-assembly modification of Bordetella bronchiseptica O polysaccharide by a novel periplasmic enzyme encoded by wbmE.
abstract: Bordetella bronchiseptica is a pathogen of humans and animals that colonizes the respiratory tract. It produces a lipopolysaccharide O antigen that contains a homopolymer of 2,3-dideoxy-2,3-diacetamido-L-galacturonic acid (L-GalNAc3NAcA). Some of these sugars are found in the uronamide form (L-GalNAc3NAcAN), and there is no discernible pattern in the distribution of amides along the chain. A B. bronchiseptica wbmE mutant expresses an O polysaccharide unusually rich in uronamides. The WbmE protein localizes to the periplasm and catalyzes the deamidation of uronamide-rich O chains in lipopolysaccharide purified from the mutant, to attain a wild-type uronamide/uronic acid ratio. WbmE is a member of the papain-like transglutaminase superfamily, and this categorization is consistent with a deamidase role. The periplasmic location of WbmE and its acceptance of complete lipopolysaccharide as substrate indicate that it operates at a late stage in lipopolysaccharide biosynthesis, after polymerization and export of the O chain from the cytoplasm. This is the first report of such a modification of O antigen after assembly. The expression of wbmE is controlled by the Bordetella virulence gene two-component regulatory system, BvgAS, suggesting that this deamidation is a novel mechanism by which these bacteria modify their cell surface charge in response to environmental stimuli.
authors.affiliation: Department of Veterinary Medicine, University of Cambridge, Cambridge CB3 0ES, United Kingdom. jeguel@gmail.com
authors.forename: Jerry D
authors.initials: JD
authors.lastname: King
authors.forename: Evgeny
authors.initials: E
authors.lastname: Vinogradov
authors.forename: Andrew
authors.initials: A
authors.lastname: Preston
authors.forename: Jianjun
authors.initials: J
authors.lastname: Li
authors.forename: Duncan J
authors.initials: DJ
authors.lastname: Maskell
mesh_terms: D000581:Amidohydrolases / Q000235:genetics / Q000378:metabolism*; D016950:Bordetella bronchiseptica / Q000201:enzymology* / Q000235:genetics; D003593:Cytoplasm / Q000201:enzymology / Q000235:genetics; D019081:O Antigens / Q000096:biosynthesis* / Q000235:genetics; D033903:Periplasmic Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D019081:O Antigens; D033903:Periplasmic Proteins; D000581:Amidohydrolases