NanC Crystal Structure, a Model for Outer-Membrane Channels of the Acidic Sugar-Specific KdgM Porin Family |
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Authors: | Christophe Wirth Céline Boiteux Tilman Schirmer |
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Institution: | 1 Department of Structural Biology, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland 2 Université de Lyon, F-69003; Université Lyon 1, F-69622; INSA-Lyon, Villeurbanne, F-69621; CNRS, UMR5240, Microbiologie Adaptation et Pathogénie, France 3 Swiss Institute of Bioinformatics, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland |
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Abstract: | Sialic acids are acidic sugars present mostly on vertebrate cell surfaces, which can be metabolized by bacteria and act as an inflammation signal. N-Acetylneuraminic acid, the most abundant sialic acid, can enter into Escherichia coli K12 through NanC, an N-acetylneuraminic acid-inducible outer-membrane channel. With its 215 residues, NanC belongs to the family of small monomeric KdgM-related porins. KdgM homologues are found in gammaproteobacteria, including major plant and human pathogens, and together they define a large family of putative acidic sugar/oligosaccharide transporters, which are as yet poorly characterized. Here, we present the first high-resolution structure of a KdgM family member. NanC folds into a 28-Å-high, 12-stranded β-barrel, resembling the β-domain of autotransporter NalP and defining an open pore with an average radius of 3.3 Å. The channel is lined by two strings of basic residues facing each other across the pore, a feature that appears largely conserved within the KdgM family and is likely to facilitate the diffusion of acidic oligosaccharides. |
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Keywords: | OPOE octylpolyoxyethylene GAn oligogalacturonate MIRAS multiple isomorphous replacement with anomalous scattering LDAO lauryldimethylamine-N-oxide Neu5Ac N-acetylneuraminic acid IB-NanC inclusion body-targeted NanC Mb-NanC outer membrane-targeted NanC |
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