New Proteins Involved in Sulfur Trafficking in the Cytoplasm of Allochromatium vinosum

Abstract

Background: Sulfur carrier proteins Rhd_2599, TusA, and DsrE2 occur in many sulfur oxidizing prokaryotes. Results: Rhd_2599, TusA, and possibly DsrE2 are involved in cytoplasmic sulfur trafficking during dissimilatory sulfur oxidation. Conclusion: Sulfur transfer from persulfide intermediates to dissimilatory sulfite reductase involves Rhd_2599, TusA, and possibly DsrE2. Significance: Proteins involved in dissimilatory sulfur oxidation have been identified.

Cytoplasmic sulfur trafficking in sulfur‐oxidizing prokaryotes

“…The protein from A. vinosum (Alvin_2599) is a soluble monomer and catalyzes sulfur transfer from thiosulfate or GSSH to cyanide in vitro . Mass spectrometry verified the transfer of sulfane sulfur from both substrates to the conserved active site of cysteine but not to a second only partly conserved cysteine . Most importantly, TusA was clearly established as a protein accepting sulfane sulfur from the A. vinosum rhodanese.…”

“…The A. vinosum protein (Alvin_2601)‐encoded downstream of the rhd‐tusA genes falls into group DsrE2A with the active site cysteine present as the second in a conserved Cys‐X 9 ‐Cys motif. Recombinant A. vinosum DsrE2A is an experimentally established membrane protein with two predicted transmembrane helices arranged such that the carboxy‐terminal part of the protein carrying one strictly conserved and two further cysteine residues is located in the cytoplasm . The same topology is predicted for the DsrE2A proteins encoded in all members of the Chromatiaceae and Acidithiobacillaceae families listed in ref.…”

“…TusA alone is incapable of mobilizing sulfur from thiosulfate or low-molecular-weight organic persulfides like glutathione persulfide (GSSH; ref. 4).…”

“…In several sulfur oxidizers including Acidithiobacillus ferrooxidans, Metallosphaera sedula, and the purple sulfur bacterium Allochromatium vinosum, relative mRNA levels for tusA were significantly higher under sulfur-oxidizing conditions than in the absence of reduced sulfur compounds (22,(31)(32)(33). An A. vinosum strain deficient of the rhd-tusA-dsrE2 genes was impaired in its ability to degrade zero-valent sulfur formed during the oxidation of sulfide and thiosulfate (4). The eminently important role of TusA is further highlighted by the finding that TusA is among the most abundant proteins in A. vinosum cells grown photolithoautotrophically on reduced sulfur compounds ( Fig.…”

“…The rhd-tusA-dsrE2 genes are cotranscribed in A. vinosum (4). In this as well as in all other cases studied, the genes follow the same pattern of transcription as observed for the established or putative cytoplasmic sulfane sulfur-oxidizing proteins (i.e., the Dsr or Hdr-like system) and other proteins involved in oxidative sulfur metabolism such as sulfur globule proteins or the enzymes of the two different cytoplasmic sulfite oxidation pathways in A. vinosum (4,22,32,33,35).…”