Structure and mechanism of the hexameric MecA-ClpC molecular machine

Nature. 2011 Mar 17;471(7338):331-5. doi: 10.1038/nature09780. Epub 2011 Mar 2.


Regulated proteolysis by ATP-dependent proteases is universal in all living cells. Bacterial ClpC, a member of the Clp/Hsp100 family of AAA+ proteins (ATPases associated with diverse cellular activities) with two nucleotide-binding domains (D1 and D2), requires the adaptor protein MecA for activation and substrate targeting. The activated, hexameric MecA-ClpC molecular machine harnesses the energy of ATP binding and hydrolysis to unfold specific substrate proteins and translocate the unfolded polypeptide to the ClpP protease for degradation. Here we report three related crystal structures: a heterodimer between MecA and the amino domain of ClpC, a heterododecamer between MecA and D2-deleted ClpC, and a hexameric complex between MecA and full-length ClpC. In conjunction with biochemical analyses, these structures reveal the organizational principles behind the hexameric MecA-ClpC complex, explain the molecular mechanisms for MecA-mediated ClpC activation and provide mechanistic insights into the function of the MecA-ClpC molecular machine. These findings have implications for related Clp/Hsp100 molecular machines.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Binding Sites
  • Crystallography, X-Ray
  • Endopeptidase Clp / metabolism
  • Heat-Shock Proteins / chemistry*
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / metabolism*
  • Hydrolysis
  • Models, Molecular
  • Protein Binding
  • Protein Conformation
  • Protein Multimerization
  • Protein Structure, Tertiary
  • Protein Unfolding
  • Substrate Specificity


  • Bacterial Proteins
  • ClpC protein, Bacteria
  • Heat-Shock Proteins
  • mecA protein, Bacillus subtilis
  • Adenosine Triphosphate
  • Endopeptidase Clp

Associated data

  • PDB/2Y1Q
  • PDB/2Y1R
  • PDB/3PXG
  • PDB/3PXI