Presenting Author:

Ekaterina Filippova, Ph.D.

Principal Investigator:

Wayne Anderson, Ph.D.

Department:

Biochemistry and Molecular Genetics

Keywords:

Rcs phosphorelay, FixJ/NarL family, RcsB, signal transduction, receiver domain, RcsAB box, flhDC

Location:

Third Floor, Feinberg Pavilion, Northwestern Memorial Hospital

B2 - Basic Science

Structural basis of DNA recognition by the response regulator RcsB

RcsB is a transcription factor of the Rcs phosphorelay two-component signal transduction system that activates transcription from more then 150 genes essential for virulence and survival of enteric pathogens. RcsB forms homo-dimers and hetero-dimers with other transcription factors that regulate transcription in both phosphorylation-dependent and independent manners. Despite increasing awareness of RcsB’s importance, the lack of structural information became a major barrier to understanding the molecular mechanisms by which RcsB binds to DNA and activates transcription. In this study, we present the crystal structure of the two-component response regulator RcsB from Escherichia coli K-12 in complex with a DNA consensus sequence called the “RcsAB box” on the flhDC operon determined at 3.6 Å resolution. The structure reveals that RcsB forms a unique asymmetric dimer in its non-phosphorylated state upon binding to DNA. In the RcsB-DNA complex structure the helices of the conserved helix-turn-helix DNA-binding motif of RcsB contact the B-DNA major groove making a few nucleotide-sequence-specific interactions. The asymmetry of the dimer and the low number of specific contacts with the bases of DNA likely give the freedom that allows RcsB to recognize different genes and form hetero-complexes with its auxiliary transcription factors. Our combined data provide valuable details of the mechanism of bacterial regulation by the Rcs system. Ultimately, the structure of the RcsB-DNA complex will serve as a template for development of novel antimicrobial compounds to treat infections caused by gram-negative pathogens.