The global repressor FliZ antagonizes gene expression by σS-containing RNA polymerase due to overlapping DNA binding specificity.
FliZ, a global regulatory protein under the control of the flagellar master regulator FlhDC, was shown to antagonize σ(S)-dependent gene expression in Escherichia coli. Thereby it plays a pivotal role in the decision between alternative life-styles, i.e. FlhDC-controlled flagellum-based motility or σ(S)-dependent curli fimbriae-mediated adhesion and biofilm formation. Here, we show that FliZ is an abundant DNA-binding protein that inhibits gene expression mediated by σ(S) by recognizing operator sequences that resemble the -10 region of σ(S)-dependent promoters. FliZ does so with a structural element that is similar to region 3.0 of σ(S). Within this element, R108 in FliZ corresponds to K173 in σ(S), which contacts a conserved cytosine at the -13 promoter position that is specific for σ(S)-dependent promoters. R108 as well as C(-13) are also crucial for DNA binding by FliZ. However, while a number of FliZ binding sites correspond to known σ(S)-dependent promoters, promoter activity is not a prerequisite for FliZ binding and repressor function. Thus, we demonstrate that FliZ also feedback-controls flagellar gene expression by binding to a site in the flhDC control region that shows similarity only to a -10 element of a σ(S)-dependent promoter, but does not function as a promoter.
Institut für Biologie-Mikrobiologie, Freie Universität Berlin, Königin-Luise-Strasse 12-16, 14195 Berlin, Germany.
Christina
C
Pesavento
Regine
R
Hengge
D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001665:Binding Sites; D004269:DNA, Bacterial / Q000737:chemistry / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D009876:Operon; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism*; D012808:Sigma Factor / Q000037:antagonists & inhibitors / Q000378:metabolism*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C574299:FliZ protein, E coli; D012097:Repressor Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D012321:DNA-Directed RNA Polymerases