Molecular mechanism of energy conservation in polysulfide respiration

Nat Struct Mol Biol. 2008 Jul;15(7):730-7. doi: 10.1038/nsmb.1434. Epub 2008 Jun 8.


Bacterial polysulfide reductase (PsrABC) is an integral membrane protein complex responsible for quinone-coupled reduction of polysulfide, a process important in extreme environments such as deep-sea vents and hot springs. We determined the structure of polysulfide reductase from Thermus thermophilus at 2.4-A resolution, revealing how the PsrA subunit recognizes and reduces its unique polyanionic substrate. The integral membrane subunit PsrC was characterized using the natural substrate menaquinone-7 and inhibitors, providing a comprehensive representation of a quinone binding site and revealing the presence of a water-filled cavity connecting the quinone binding site on the periplasmic side to the cytoplasm. These results suggest that polysulfide reductase could be a key energy-conserving enzyme of the T. thermophilus respiratory chain, using polysulfide as the terminal electron acceptor and pumping protons across the membrane via a previously unknown mechanism.

Publication types

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

MeSH terms

  • Binding Sites
  • Catalytic Domain
  • Cell Membrane / enzymology
  • Dimerization
  • Electron Transport
  • Electrons
  • Energy Metabolism*
  • Models, Molecular
  • Oxidoreductases / chemistry
  • Oxidoreductases / metabolism*
  • Protein Structure, Secondary
  • Protein Subunits / chemistry
  • Protein Subunits / metabolism
  • Protons
  • Quinones / metabolism
  • Static Electricity
  • Sulfides / metabolism*
  • Thermus thermophilus / enzymology*


  • Protein Subunits
  • Protons
  • Quinones
  • Sulfides
  • polysulfide
  • Oxidoreductases
  • polysulfide reductase