Flagellar operons are divided into three classes with respect to their transcriptional hierarchy in Salmonella enterica serovar Typhimurium. The class 1 gene products FlhD and FlhC act together in an FlhD2C2 heterotetramer, which binds upstream of the class 2 promoters to facilitate binding of RNA polymerase. Class 2 expression is known to be enhanced by a disruption mutation in a flagellar gene, fliT. In this study, we purified FliT protein in a His-tagged form and showed that the protein prevented binding of FlhD2C2 to the class 2 promoter and inhibited FlhD 2C2-dependent transcription. Pull-down and far-Western blotting analyses revealed that the FliT protein was capable of binding to FlhD2C2 and FlhC and not to FlhD alone. We conclude that FliT acts as an anti-FlhD2C2 factor, which binds to FlhD2C2 through interaction with the FlhC subunit and inhibits its binding to the class 2 promoter.
ASJC Scopus subject areas
- Molecular Biology