Intermediates in the Sox Sulfur Oxidation Pathway Are Bound to a Sulfane Conjugate of the Carrier Protein SoxYZ

PLoS One. 2017 Mar 3;12(3):e0173395. doi: 10.1371/journal.pone.0173395. eCollection 2017.


The Sox pathway found in many sulfur bacteria oxidizes thiosulfate to sulfate. Pathway intermediates are covalently bound to a cysteine residue in the carrier protein SoxYZ. We have used biochemical complementation by SoxYZ-conjugates to probe the identity of the intermediates in the Sox pathway. We find that unconjugated SoxYZ and SoxYZ-S-sulfonate are unlikely to be intermediates during normal turnover in disagreement with current models. By contrast, conjugates with multiple sulfane atoms are readily metabolised by the Sox pathway. The most parsimonious interpretation of these data is that the true carrier species in the Sox pathway is a SoxYZ-S-sulfane adduct.

MeSH terms

  • Bacteria / enzymology*
  • Carrier Proteins / chemistry
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cysteine / metabolism
  • Oxidation-Reduction
  • Oxidoreductases Acting on Sulfur Group Donors / chemistry
  • Oxidoreductases Acting on Sulfur Group Donors / metabolism*
  • Protein Binding
  • Signal Transduction
  • Sulfur / metabolism*
  • Thiosulfates / chemistry
  • Thiosulfates / metabolism


  • Carrier Proteins
  • Thiosulfates
  • Sulfur
  • Oxidoreductases Acting on Sulfur Group Donors
  • Cysteine

Grant support

This work was supported by Biotechnology and Biological Research Council (GB) through a studentship to DBG. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.