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Sialic Acid Mutarotation Is Catalyzed by the Escherichia coli β-Propeller Protein YjhT

Severi, Emmanuele and Müller, Axel and Potts, Jennifer R. and Leech, Andrew and Williamson, David and Wilson, Keith S. and Thomas, Gavin H. (2008) Sialic Acid Mutarotation Is Catalyzed by the Escherichia coli β-Propeller Protein YjhT. Journal of Biological Chemistry, 283 (8). pp. 4841-4849. ISSN 0021-9258. doi:10.1074/jbc.M707822200.

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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 β-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 β-anomers of the sialic acid N-acetylneuraminic acid, thus describing a novel sialic acid mutarotase activity. The structure of this periplasmic protein, solved to 1.5Å resolution, reveals a dimeric 6-bladed unclosed β-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.

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Additional Information:© 2008 the American Society for Biochemistry and Molecular Biology. Received for publication, September 18, 2007 , and in revised form, November 26, 2007. Originally published In Press as doi:10.1074/jbc.M707822200 on December 5, 2007. We thank the ESRF, Grenoble, France, for excellent data collection facilities; Prof. Hirotada Mori and Prof. Simon Andrews for E. coli Keio strains; Berni Strongitharm for help with the electrospray ionization-mass spectrometry; and Dr. Christoph Baumann for help in preparation of a figure. The atomic coordinates and structure factors (code 2uvk) have been deposited in the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ ( This work was supported by the Biotechnology and Biological Sciences Research Council. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. The on-line version of this article (available at contains supplemental Experimental Procedures, additional references, Table 1, and Figs. 1, 2, 3, 4, 5, 6, 7, 8.
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Biotechnology and Biological Sciences Research Council (BBSRC)UNSPECIFIED
Issue or Number:8
Record Number:CaltechAUTHORS:SEVjbc08
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ID Code:9622
Deposited By: Archive Administrator
Deposited On:19 Feb 2008
Last Modified:08 Nov 2021 21:00

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