Effects of DksA, GreA, and GreB on transcription initiation: insights into the mechanisms of factors that bind in the secondary channel of RNA polymerase.

ABSTRACT: Escherichia coli DksA, GreA, and GreB have similar structures and bind to the same location on RNA polymerase (RNAP), the secondary channel. We show that GreB can fulfil some roles of DksA in vitro, including shifting the promoter-open complex equilibrium in the dissociation direction, thus allowing rRNA promoters to respond to changes in the concentration of ppGpp and NTPs. However, unlike deletion of the dksA gene, deletion of greB had no effect on rRNA promoters in vivo. We show that the apparent affinities of DksA and GreB for RNAP are similar, but the cellular concentration of GreB is much lower than that of DksA. When over-expressed and in the absence of competing GreA, GreB almost completely complemented the loss of dksA in control of rRNA expression, indicating its inability to reg

SUBMITTER: Rutherford ST 

PROVIDER: S-EPMC1839928 | biostudies-literature | 2007 Mar

REPOSITORIES: biostudies-literature