z-logo
Premium
Thiosulfate dehydrogenase: a widespread unusual acidophilic c ‐type cytochrome
Author(s) -
Denkmann Kevin,
Grein Fabian,
Zigann Renate,
Siemen Anna,
Bergmann Johannes,
van Helmont Sebastian,
Nicolai Anne,
Pereira Inês A. C.,
Dahl Christiane
Publication year - 2012
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2012.02820.x
Subject(s) - thiosulfate , tetrathionate , biochemistry , biology , cysteine , histidine , sulfur , dehydrogenase , sulfur metabolism , escherichia coli , cytochrome , enzyme , stereochemistry , chemistry , gene , organic chemistry
Summary In this work we identified the gene for the tetrathionate‐forming thiosulfate dehydrogenase (TsdA) from the purple sulfur bacterium Allochromatium vinosum by sequence analysis and reverse genetics. The recombinant protein produced in Escherichia coli is a periplasmic, monomeric 25.8 kDa dihaem cytochrome c with an enzyme activity optimum at pH 4. UV‐visible and electron paramagnetic resonance spectroscopy indicate methionine (strictly conserved M 222 or M 236 ) and cysteine (C 123 ) as probable sixth distal axial ligands of the two haem irons in TsdA. These results place TsdA in the group of c ‐type cytochromes with an unusual axial histidine‐cysteine coordination of the haem iron. These proteins appear to play a pivotal role in sulfur‐based energy metabolism. Exchange of C 123 to glycine rendered thiosulfate dehydrogenase inactive, proving the importance of this residue for catalysis. TsdA homologues are present in α ‐, β ‐, δ ‐, γ ‐ and ε‐Proteobacteria . Three of these were produced in E. coli and exhibited the expected enzymatic activity. The widespread occurrence of tsdA agrees with reports of tetrathionate formation not only by specialized sulfur oxidizers but also by many chemoorganoheterotrophs that use thiosulfate as a supplemental but not as the sole energy source.

This content is not available in your region!

Continue researching here.

Having issues? You can contact us here