Structural basis for the activation mechanism of the PlcR virulence regulator by the quorum-sensing signal peptide PapR

Proc Natl Acad Sci U S A. 2013 Jan 15;110(3):1047-52. doi: 10.1073/pnas.1213770110. Epub 2012 Dec 31.


The quorum-sensing regulator PlcR is the master regulator of most known virulence factors in Bacillus cereus. It is a helix-turn-helix (HTH)-type transcription factor activated upon binding of its cognate signaling peptide PapR on a tetratricopeptide repeat-type regulatory domain. The structural and functional properties of PlcR have defined a new family of sensor regulators, called the RNPP family (for Rap, NprR, PrgX, and PlcR), in Gram-positive bacteria. To fully understand the activation mechanism of PlcR, we took a closer look at the conformation changes induced upon binding of PapR and of its target DNA, known as PlcR-box. For that purpose we have determined the structures of the apoform of PlcR (Apo PlcR) and of the ternary complex of PlcR with PapR and the PlcR-box from the plcA promoter. Comparison of the apoform of PlcR with the previously published structure of the PlcR-PapR binary complex shows how a small conformational change induced in the C-terminal region of the tetratricopeptide repeat (TPR) domain upon peptide binding propagates via the linker helix to the N-terminal HTH DNA-binding domain. Further comparison with the PlcR-PapR-DNA ternary complex shows how the activation of the PlcR dimer allows the linker helix to undergo a drastic conformational change and subsequent proper positioning of the HTH domains in the major groove of the two half sites of the pseudopalindromic PlcR-box. Together with random mutagenesis experiments and interaction measurements using peptides from distinct pherogroups, this structural analysis allows us to propose a molecular mechanism for this functional switch.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Apoproteins / chemistry
  • Apoproteins / genetics
  • Apoproteins / metabolism
  • Bacillus cereus / genetics
  • Bacillus cereus / metabolism
  • Bacillus thuringiensis / genetics
  • Bacillus thuringiensis / metabolism
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Base Sequence
  • Binding Sites
  • Crystallography, X-Ray
  • DNA, Bacterial / chemistry
  • DNA, Bacterial / genetics
  • Genes, Bacterial
  • Models, Molecular
  • Molecular Sequence Data
  • Promoter Regions, Genetic
  • Protein Conformation
  • Protein Interaction Domains and Motifs
  • Protein Multimerization
  • Quorum Sensing
  • Sequence Homology, Amino Acid
  • Static Electricity
  • Trans-Activators / chemistry*
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*
  • Virulence


  • Apoproteins
  • Bacterial Proteins
  • DNA, Bacterial
  • PapR protein, Bacillus cereus
  • PlcR protein, Bacillus
  • Trans-Activators

Associated data

  • PDB/3U3W
  • PDB/4FSC