Function and Expression of an N -Acetylneuraminic Acid-Inducible Outer Membrane Channel in Escherichia coli

• DOI: 10.1128/jb.187.6.1959-1965.2005
• Publication Date: 2005-03-02T18:50:00Z
• Authors: Guy Condemine; Catherine Berrier; Jacqueline Plumbr...; Alexandre Ghazi
• Keywords: 0301 basic medicine; Base Sequence; Escherichia coli Proteins; Molecular Sequence Data; Porins; Gene Expression Regulation, Bacterial; N-Acetylneuraminic Acid; 3. Good health; 03 medical and health sciences; Escherichia coli; Promoter Regions, Genetic; Bacterial Outer Membrane Proteins

ABSTRACT

The Escherichia coli yjhA (renamed nanC) gene encodes a protein of the KdgM family of outer membrane-specific channels. It is transcribed divergently from fimB , a gene involved in the site-specific inversion of the region controlling transcription of the fimbrial structural genes but is separated from it by one of the largest intergenic regions in E. coli . We show that nanC expression is induced by N -acetylneuraminic acid and modulated by N -acetylglucosamine. This regulation occurs via the NanR and NagC regulators, which also control fimB expression. nanC expression is also activated by the regulators cyclic AMP-catabolite activator protein, OmpR, and CpxR. When the NanC protein was reconstituted into liposomes, it formed channels with a conductance of 450 pS at positive potential and 300 to 400 pS at negative potential in 800 mM KCl. The channels had a weak anionic selectivity. In an ompR background, where the general porins OmpF and OmpC are absent, NanC is required for growth of E. coli on N -acetylneuraminic acid as the sole carbon source. All these results suggest that NanC is an N -acetylneuraminic acid outer membrane channel protein.