1. Bicarbonate-Mediated Stimulation of RegA, the Global Virulence Regulator from Citrobacter rodentium
- Author
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Yang, Ji, Dogovski, Con, Hocking, Dianna, Tauschek, Marija, Perugini, Matt, and Robins-Browne, Roy M.
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BICARBONATE ions , *MICROBIAL virulence , *CITROBACTER , *GENE expression , *ESCHERICHIA coli , *CARRIER proteins - Abstract
Abstract: The global virulence regulatory protein RegA, an AraC-like regulator, controls the expression of more than 60 genes in the mouse enteric pathogen Citrobacter rodentium. In the presence of bicarbonate, RegA activates the transcription of a number of virulence determinants and inhibits the expression of a series of housekeeping genes. To elucidate the molecular mechanism by which bicarbonate stimulates RegA activity, we carried out biophysical and mutational analyses. Our data indicate that RegA exists as a dimer in solution regardless of bicarbonate concentration. A leucine zipper, located in the region downstream of the N-terminal domain, is responsible for dimerisation. The N-terminal arm itself is involved in modulating the response to bicarbonate, which appears to bind to a region comprising a series of β-sheets within the N-terminal domain. The presence of bicarbonate relieves the autoinhibition of RegA activity by its N-terminal arm. RegA is the first example of a bacterial virulence regulator that utilises the light switch mechanism, previously described for the Escherichia coli AraC protein, to respond to a gut-associated effector that controls its activity. [Copyright &y& Elsevier]
- Published
- 2009
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