PMID:18063573
| Citation |
Severi, E, Müller, A, Potts, JR, Leech, A, Williamson, D, Wilson, KS and Thomas, GH (2008) Sialic acid mutarotation is catalyzed by the Escherichia coli beta-propeller protein YjhT. J. Biol. Chem. 283:4841-9 |
|---|---|
| Abstract |
The acquisition of host-derived sialic acid is an important virulence factor for some bacterial pathogens, but in vivo this sugar acid is sequestered in sialoconjugates as the alpha-anomer. In solution, however, sialic acid is present mainly as the beta-anomer, formed by a slow spontaneous mutarotation. We studied the Escherichia coli protein YjhT as a member of a family of uncharacterized proteins present in many sialic acid-utilizing pathogens. This protein is able to accelerate the equilibration of the alpha- and beta-anomers of the sialic acid N-acetylneuraminic acid, thus describing a novel sialic acid mutarotase activity. The structure of this periplasmic protein, solved to 1.5A resolution, reveals a dimeric 6-bladed unclosed beta-propeller, the first of a bacterial Kelch domain protein. Mutagenesis of conserved residues in YjhT demonstrated an important role for Glu-209 and Arg-215 in mutarotase activity. We also present data suggesting that the ability to utilize alpha-N-acetylneuraminic acid released from complex sialoconjugates in vivo provides a physiological advantage to bacteria containing YjhT. |
| Links |
PubMed Online version:10.1074/jbc.M707822200 |
| Keywords |
Carbohydrate Epimerases/chemistry; Carbohydrate Epimerases/genetics; Carbohydrate Epimerases/metabolism; Catalysis; Crystallography, X-Ray; Escherichia coli K12/enzymology; Escherichia coli K12/genetics; Escherichia coli K12/pathogenicity; Escherichia coli Proteins/chemistry; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; N-Acetylneuraminic Acid/chemistry; N-Acetylneuraminic Acid/genetics; N-Acetylneuraminic Acid/metabolism; Protein Structure, Tertiary; Virulence Factors/chemistry; Virulence Factors/genetics; Virulence Factors/metabolism |
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