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author:("Shi, wenchuan")
1.  Oligomerization of the Response Regulator ComE from Streptococcus mutans Is Affected by Phosphorylation 
Journal of Bacteriology  2012;194(5):1127-1135.
We have previously characterized the interactions of the response regulator ComE from Streptococcus mutans and DNA binding sites through DNase I footprinting and electrophoretic mobility shift assay analysis. Since response regulator functions are often affected by their phosphorylation state, we investigated how phosphorylation affects the biochemical function of ComE. Unlike many response regulators, we found that the phosphorylation state of ComE does not likely play a role in DNA binding affinity but rather seems to induce the formation of an oligomeric form of the protein. The role of this oligomerization state for ComE function is discussed.
doi:10.1128/JB.06565-11
PMCID: PMC3294772  PMID: 22210762
2.  Characterization of DNA Binding Sites of the ComE Response Regulator from Streptococcus mutans▿† 
Journal of Bacteriology  2011;193(14):3642-3652.
In Streptococcus mutans, both competence and bacteriocin production are controlled by ComC and the ComED two-component signal transduction system. Recent studies of S. mutans suggested that purified ComE binds to two 11-bp direct repeats in the nlmC-comC promoter region, where ComE activates nlmC and represses comC. In this work, quantitative binding studies and DNase I footprinting analysis were performed to calculate the equilibrium dissociation constant and further characterize the binding site of ComE. We found that ComE protects sequences inclusive of both direct repeats, has an equilibrium dissociation constant in the nanomolar range, and binds to these two direct repeats cooperatively. Furthermore, similar direct repeats were found upstream of cslAB, comED, comX, ftf, vicRKX, gtfD, gtfB, gtfC, and gbpB. Quantitative binding studies were performed on each of these sequences and showed that only cslAB has a similar specificity and high affinity for ComE as that seen with the upstream region of comC. A mutational analysis of the binding sequences showed that ComE does not require both repeats to bind DNA with high affinity, suggesting that single site sequences in the genome may be targets for ComE-mediated regulation. Based on the mutational analysis and DNase I footprinting analysis, we propose a consensus ComE binding site, TCBTAAAYSGT.
doi:10.1128/JB.00155-11
PMCID: PMC3133340  PMID: 21602345

Results 1-2 (2)