The c-di-GMP binding protein YcgR controls flagellar motor direction and speed to affect chemotaxis by a "backstop brake" mechanism

Mol Cell. 2010 Apr 9;38(1):128-39. doi: 10.1016/j.molcel.2010.03.001. Epub 2010 Mar 25.


We describe a mechanism of flagellar motor control by the bacterial signaling molecule c-di-GMP, which regulates several cellular behaviors. E. coli and Salmonella have multiple c-di-GMP cyclases and phosphodiesterases, yet absence of a specific phosphodiesterase YhjH impairs motility in both bacteria. yhjH mutants have elevated c-di-GMP levels and require YcgR, a c-di-GMP-binding protein, for motility inhibition. We demonstrate that YcgR interacts with the flagellar switch-complex proteins FliG and FliM, most strongly in the presence of c-di-GMP. This interaction reduces the efficiency of torque generation and induces CCW motor bias. We present a "backstop brake" model showing how both effects can result from disrupting the organization of the FliG C-terminal domain, which interacts with the stator protein MotA to generate torque. Inhibition of motility and chemotaxis may represent a strategy to prepare for sedentary existence by disfavoring migration away from a substrate on which a biofilm is to be formed.

Publication types

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

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Biofilms
  • Chemotaxis / physiology*
  • Cyclic GMP / analogs & derivatives
  • Cyclic GMP / metabolism
  • Escherichia coli / cytology
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / metabolism*
  • Flagella / metabolism*
  • Models, Molecular
  • Molecular Motor Proteins / genetics
  • Molecular Motor Proteins / metabolism*
  • Point Mutation
  • Protein Binding
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Torque


  • Bacterial Proteins
  • Escherichia coli Proteins
  • Flig protein, Bacteria
  • Molecular Motor Proteins
  • MotA protein, Bacteria
  • Recombinant Fusion Proteins
  • YcgR protein, E coli
  • YhjH protein, E coli
  • FliM protein, Bacteria
  • bis(3',5')-cyclic diguanylic acid
  • Cyclic GMP