Bicarbonate-mediated stimulation of RegA, the global virulence regulator from Citrobacter rodentium.
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 beta-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.
Department of Microbiology and Immunology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria 3010, Australia.
Ji
J
Yang
Con
C
Dogovski
Dianna
D
Hocking
Marija
M
Tauschek
Matt
M
Perugini
Roy M
RM
Robins-Browne
D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000737:chemistry; D001639:Bicarbonates / Q000378:metabolism*; D002942:Circular Dichroism; D044082:Citrobacter rodentium / Q000187:drug effects* / Q000502:physiology; D004252:DNA Mutational Analysis; D019281:Dimerization; D015964:Gene Expression Regulation, Bacterial; D016350:Leucine Zippers; D008958:Models, Molecular; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D017433:Protein Structure, Secondary; D013057:Spectrum Analysis; D015533:Transcriptional Activation; D037521:Virulence Factors / Q000096:biosynthesis*
D001426:Bacterial Proteins; D001639:Bicarbonates; C072722:RegA protein, Bacteria; D037521:Virulence Factors