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Repression of galP , the galactose transporter in Escherichia coli , requires the specific regulator of N ‐acetylglucosamine metabolism
Author(s) -
El Qaidi Samir,
Allemand Frédéric,
Oberto Jacques,
Plumbridge Jacqueline
Publication year - 2009
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2008.06515.x
Subject(s) - lac repressor , biology , galactose , escherichia coli , repressor , beta galactosidase , psychological repression , biochemistry , mutation , gene , microbiology and biotechnology , gene expression
Summary Soupene et al . [ J. Bacteriol. (2003) 185 5611–5626] made the unexpected observation that the presence of a mutation, in the gene for the N ‐acetylglucosamine repressor, nagC , increased the growth rate of Escherichia coli MG1655 on galactose, an unrelated sugar. We have found that NagC, binds to a single, high‐affinity site overlapping the promoter of galP (galactose permease) gene and that expression of galP is repressed by a combination of NagC, GalR and GalS. In addition to the previously identified galOE operator, other gal operators further upstream are required for full repression. GalS has a specific role, as it binds with higher affinity to one of the upstream operators but its effect in vivo is only observed in the presence of GalR. Regulation of galP by three specific repressors, NagC, GalR and GalS is unusual in that it involves multiple, specific regulators from two different areas of metabolism. This novel regulation seems to be particular for E. coli and its nearest neighbour, Shigella. Other bacteria with galP orthologues, although retaining the metK‐galP gene order, do not have the NagC site. Although quantitative effects were strain specific, nagC mutations increased the growth rate on galactose of all E. coli strains tested.