Structural and Molecular Genetic Insight into a Widespread Sulfur Oxidation Pathway

Christiane Dahl, Andrea Schulte, Yvonne Stockdreher, Connie Hong, Frauke Grimm, Johannes Sander, Rosalind Kim, Sung Hou Kim, Dong Hae Shin

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50 Scopus citations


Many environmentally important photo- and chemolithoautotrophic bacteria accumulate globules of polymeric, water-insoluble sulfur as a transient product during oxidation of reduced sulfur compounds. Oxidation of this sulfur requires the concerted action of Dsr proteins. However, individual functions and interplay of these proteins are largely unclear. We proved with a ΔdsrE mutant experiment that the cytoplasmic α2β2γ2-structured protein DsrEFH is absolutely essential for the oxidation of sulfur stored in the intracellular sulfur globules of the purple sulfur bacterial model organism Allochromatium vinosum. The ability to degrade stored sulfur was fully regained upon complementation with dsrEFH in trans. The crystal structure of DsrEFH was determined at 2.5 Å resolution to assist functional assignment in detail. In conjunction with phylogenetic analyses, two different types of putative active sites were identified in DsrE and DsrH and shown to be characteristic for sulfur-oxidizing bacteria. Conserved Cys78 of A. vinosum DsrE corresponds to the active cysteines of Escherichia coli YchN and TusD. TusBCD and the protein TusE are parts of sulfur relay system involved in thiouridine biosynthesis. DsrEFH interacts with DsrC, a TusE homologue encoded in the same operon. The conserved penultimate cysteine residue in the carboxy-terminus of DsrC is essential for the interaction. Here, we show that Cys78 of DsrE is strictly required for interaction with DsrC while Cys20 in the putative active site of DsrH is dispensable for that reaction. In summary, our findings point at the occurrence of sulfur transfer reactions during sulfur oxidation via the Dsr proteins.

Original languageEnglish
Pages (from-to)1287-1300
Number of pages14
JournalJournal of Molecular Biology
Issue number5
StatePublished - 31 Dec 2008

Bibliographical note

Funding Information:
Skillful technical assistance by Hisao Yokota, Jaru Jancarik, and Birgitt Hüttig is gratefully acknowledged. The biochemical and genetic parts of this research were supported by the Deutsche Forschungsgemeinschaft (grants Da 351/3-3, 3-4, and 3-5 to C.D.). The crystallographic part described here was supported by the Korea Research Foundation Grant funded by the Korean Government (Ministry of Education and Human Resource Development, Basic Research Promotion Fund, KRF-2007-313-C00618), by Grant No. R15-2006-020 from the National Core Research Center program of the Ministry of Science and Technology and Korea Science and Engineering Foundation through the Center for Cell Signaling and Drug Discovery Research at Ewha Womans University, and by the Protein Structure Initiative grant from National Institutes of Health GM 62412.


  • DsrEFH
  • anoxygenic phototrophic sulfur bacteria YchN fold
  • crystal structure
  • dissimilatory sulfite reductase
  • dissimilatory sulfur oxidation


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