Structural basis for the oxidation of thiosulfate by a sulfur cycle enzyme

V A Bamford, S Bruno, Tim Rasmussen, C Appia-Ayme, M R Cheesman, B C Berks, A M Hemmings

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Abstract

Reduced inorganic sulfur compounds are utilized by many bacteria as electron donors to photosynthetic or respiratory electron transport chains. This metabolism is a key component of the biogeochemical sulfur cycle. The SoxAX protein is a heterodimeric c-type cytochrome involved in thiosulfate oxidation. The crystal structures of SoxAX from the photosynthetic bacterium Rhodovulum sulfidophilum have been solved at 1.75 Angstrom resolution in the oxidized state and at 1.5 Angstrom resolution in the dithionite-reduced state, providing the first structural insights into the enzymatic oxidation of thiosulfate. The SoxAX active site contains a haem with unprecedented cysteine persulfide (cysteine sulfane) coordination. This unusual post-translational modification is also seen in sulfurtransferases such as rhodanese. Intriguingly, this enzyme shares further active site characteristics with SoxAX such as an adjacent conserved arginine residue and a strongly positive electrostatic potential. These similarities have allowed us to suggest a catalytic mechanism for enzymatic thiosulfate oxidation. The atomic coordinates and experimental structure factors have been deposited in the PDB with the accession codes 1H31, 1H32 and 1H33.

Original languageEnglish
Pages (from-to)5599-5610
Number of pages12
JournalEMBO Journal
Volume21
Issue number21
DOIs
Publication statusPublished - 1 Nov 2002

Keywords

  • cysteine persulfide haem ligand
  • SoxAX complex
  • sulfur cycle
  • thiosulfate oxidation
  • X-ray crystal structure
  • PARACOCCUS-PANTOTROPHUS GB17
  • CYSTATHIONINE BETA-SYNTHASE
  • CYTOCHROME-C PEROXIDASE
  • CRYSTAL-STRUCTURE
  • RHODOVULUM-SULFIDOPHILUM
  • ACTIVE-SITE
  • PROTEIN
  • HEME
  • BACTERIUM
  • RHODANESE
  • X-ray crystal structure

Cite this

Bamford, V. A., Bruno, S., Rasmussen, T., Appia-Ayme, C., Cheesman, M. R., Berks, B. C., & Hemmings, A. M. (2002). Structural basis for the oxidation of thiosulfate by a sulfur cycle enzyme. EMBO Journal, 21(21), 5599-5610. https://doi.org/10.1093/emboj/cdf566