Trinuclear copper biocatalytic center forms an active site of thiocyanate dehydrogenase

Proc Natl Acad Sci U S A. 2020 Mar 10;117(10):5280-5290. doi: 10.1073/pnas.1922133117. Epub 2020 Feb 24.


Biocatalytic copper centers are generally involved in the activation and reduction of dioxygen, with only few exceptions known. Here we report the discovery and characterization of a previously undescribed copper center that forms the active site of a copper-containing enzyme thiocyanate dehydrogenase (suggested EC that was purified from the haloalkaliphilic sulfur-oxidizing bacterium of the genus Thioalkalivibrio ubiquitous in saline alkaline soda lakes. The copper cluster is formed by three copper ions located at the corners of a near-isosceles triangle and facilitates a direct thiocyanate conversion into cyanate, elemental sulfur, and two reducing equivalents without involvement of molecular oxygen. A molecular mechanism of catalysis is suggested based on high-resolution three-dimensional structures, electron paramagnetic resonance (EPR) spectroscopy, quantum mechanics/molecular mechanics (QM/MM) simulations, kinetic studies, and the results of site-directed mutagenesis.

Keywords: EPR; copper centers; crystal structure; molecular mechanism; thiocyanate dehydrogenase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / chemistry*
  • Biocatalysis
  • Catalytic Domain*
  • Copper / chemistry*
  • Ectothiorhodospiraceae / enzymology*
  • Electron Spin Resonance Spectroscopy
  • Hydrogen-Ion Concentration
  • Oxidation-Reduction
  • Oxidoreductases / chemistry*
  • Oxygen / chemistry
  • Sulfur / chemistry
  • Sulfur-Reducing Bacteria / enzymology*


  • Bacterial Proteins
  • Sulfur
  • Copper
  • Oxidoreductases
  • Oxygen

Supplementary concepts

  • Thioalkalivibrio paradoxus
  • Thioalkalivibrio thiocyanoxidans

Associated data

  • PDB/6I3Q
  • PDB/6UWE
  • PDB/6SJI
  • PDB/6G50