Structure of the Escherichia coli FlhDC complex, a prokaryotic heteromeric regulator of transcription

J Mol Biol. 2006 Jan 27;355(4):798-808. doi: 10.1016/j.jmb.2005.11.020. Epub 2005 Nov 22.


The hetero-oligomeric complex of the FlhD and FlhC proteins (FlhDC) regulates transcription from several flagellar and non-flagellar operons in bacteria. The crystallographic structure of the Escherichia coli FlhDC complex has been solved to 3.0 A resolution, revealing a hexameric FlhD4FlhC2 assembly. In the complex, each FlhC protomer binds an FlhD2 dimer; the conformation of the dimer in the complex differs significantly from its conformation in the absence of FlhC. FlhC has a novel tertiary fold that includes a heretofore unrecognized zinc-binding site in which the ion is ligated by four cysteine residues. Gel shift experiments show that binding of the FlhDC complex to a cognate promoter bends the DNA by approximately 111 degrees . The structure of the FlhDC complex is compatible with models in which a fragment of operator DNA, at least 48 base-pairs in length, wraps around the complex and bends significantly when binding.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Base Sequence
  • Binding Sites
  • DNA / chemistry
  • DNA / genetics
  • DNA-Binding Proteins / chemistry*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Escherichia coli / chemistry*
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Gene Expression Regulation, Bacterial*
  • Models, Molecular
  • Molecular Sequence Data
  • Protein Binding
  • Protein Folding
  • Protein Structure, Quaternary
  • Regulatory Elements, Transcriptional / genetics
  • Trans-Activators / chemistry*
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*
  • Transcription, Genetic*
  • Zinc / chemistry


  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • Trans-Activators
  • flhC protein, E coli
  • flhD protein, E coli
  • DNA
  • Zinc

Associated data

  • PDB/2AVU