UlaR is a DNA-binding transcription factor of 251 amino acids that is expressed constitutively and that coordinately represses transcription of a divergent operon (ula) involved in transport and utilization of L-ascorbate catabolism |CITS:|. Synthesis of these genes is induced when Escherichia coli is grown in the absence of glucose, and under anaerobic conditions it can ferment L-ascorbate; under aerobic conditions it is functional in the presence of casein acid hydrolysate |CITS:|.
L-Ascorbate-6-P is the effector of the UlaR transcriptional repressor, and when this small molecule binds to UlaR, it severely impairs the formation of UlaR cognate operator sites, since they form a stable complex |CITS:|. L-Ascorbate-6-P weakens the affinity of UlaR for DNA and displaces the UlaR oligomer state from a transcription-silencing tetrameric form to a transcription-activating dimeric form |CITS:|. UlaR activity is also controlled by homotypic tetramer-dimer transitions regulated by L-ascorbate-6-P |CITS:|.
UlaR binds to four inverted repeat motifs in the divergent intergenic region ulaG-ulaA and overlaps its target promoters to repress transcription by blocking the interaction of the RNA polymerase with ulaGp and ulaAp |CITS:|. Here, the presence of L-ascorbate-6-P breaks this configuration down into DNA-free UlaR homodimers and allows transcription to proceed |CITS:|.
At concentrations of >2 nM, L-ascorbate-6-P displaces UlaR from its operator site |CITS:|.Read more >
In this system the full repression of the ula regulon requires IHF and binding of UlaR to four operator sites, possibly involving UlaR-mediated DNA loop formation |CITS:|.
The UlaR transcriptional repressor belongs to the DeoR family, and accordingly, this transcriptional repressor family protein is composed of two domains: an N-terminal HTH domain (residues 1-62), which contains the DNA-binding region |CITS:|, and the C-terminal sugar-phosphate-binding domain (residues 69-251), which is responsible for dimerization and inducer binding |CITS:|. The C-terminal sugar-phosphate-binding domain belongs to the DeoR-C family of the ISOCOT superfamily and is structurally related to E. coli D-ribose-5-P isomerase |CITS:|. Asp206 and Lys209 are directly involved in binding L-ascorbate-6-P |CITS:|.
Review: |CITS: |.
|Connectivity class:||Local Regulator|
|Length:||756 bp / 251 aa|
|TU(s) encoding the TF:||
|Regulated gene(s)||ulaA, ulaB, ulaC, ulaD, ulaE, ulaF, ulaG|
|Multifun term(s) of regulated gene(s)||
MultiFun Term (List of genes associated to the multifun term)
Phosphotransferase Systems (PEP-dependent PTS) (3)
ulaA, ulaB, ulaC
unassigned reversible reactions (2)
carbon compounds (1)
carbon utilization (1)
|Regulated operon(s)||ulaABCDEF, ulaG|
|First gene in the operon(s)||ulaA, ulaG|
|Simple and complex regulons|
|Simple and complex regulatory phrases||
Regulatory phrase (List of promoters regulated by the phrase)
|Functional conformation||Function||Promoter||Sigma factor||Central Rel-Pos||Distance to first Gene||Genes||Sequence||LeftPos||RightPos||Evidence (Confirmed, Strong, Weak)||References|
|UlaR||repressor||ulaAp||Sigma70||-44.5||-97.5||ulaA, ulaB, ulaC, ulaD, ulaE, ulaF||
|4419873||4419892||[BPP], [GEA], [SM]||, , |
|UlaR||repressor||ulaAp||Sigma70||-19.5||-72.5||ulaA, ulaB, ulaC, ulaD, ulaE, ulaF||
|4419898||4419917||[BPP], [GEA]||, , |
|4419666||4419685||[BPP], [GEA]||, |
|4419641||4419660||[BPP], [GEA]||, |
|Alignment and PSSM for UlaR TFBSs|
|Aligned TFBS of UlaR|
|Position weight matrix (PWM).|
A 0 0 0 4 2 2 2 0 0 4 4 0 0 4 2 3 4 C 0 0 4 0 1 0 0 1 0 0 0 0 4 0 1 0 0 G 2 0 0 0 1 1 0 1 1 0 0 0 0 0 0 0 0 T 2 4 0 0 0 1 2 2 3 0 0 4 0 0 1 1 0
|Evolutionary conservation of regulatory elements|
 Campos E., Aguilar J., Baldoma L., Badia J., 2002, The gene yjfQ encodes the repressor of the yjfR-X regulon (ula), which is involved in L-ascorbate metabolism in Escherichia coli., J Bacteriol. 184(21):6065-8
 Campos E., Baldoma L., Aguilar J., Badia J., 2004, Regulation of expression of the divergent ulaG and ulaABCDEF operons involved in LaAscorbate dissimilation in Escherichia coli., J Bacteriol. 186(6):1720-8