Details

Autor(en) / Beteiligte

• Kappler, Ulrike
• Bernhardt, Paul V.
• Kilmartin, James
• Riley, Mark J.
• Teschner, Julia
• McKenzie, Kirsty J.
• Hanson, Graeme R.

Titel

SoxAX Cytochromes, a New Type of Heme Copper Protein Involved in Bacterial Energy Generation from Sulfur Compounds

Ist Teil von

• The Journal of biological chemistry, 2008-08, Vol.283 (32), p.22206-22214

Ort / Verlag

United States: Elsevier Inc

Erscheinungsjahr

2008

Quelle

MEDLINE

Beschreibungen/Notizen

• SoxAX cytochromes are essential for the function of the only confirmed pathway for bacterial thiosulfate oxidation, the so-called “Sox pathway,” in which they catalyze the initial formation of a S-S bond between thiosulfate and the SoxYZ carrier protein. Our work using the Starkeya novella diheme SoxAX protein reveals for the first time that in addition to two active site heme groups, SoxAX contains a mononuclear CuII center with a distorted tetragonal geometry and three to four nitrogen ligands, one of which is a histidine. The CuII center enhanced SoxAX activity in a newly developed, glutathione-based assay system that mimics the natural reaction of SoxAX with SoxYZ. EPR spectroscopy confirmed that the SoxAX CuII center is reduced by glutathione. At pH 7 a Kmapp of 0.19 ± 0.028 mm and a kcatapp of 5.7 ± 0.25s-1 were determined for glutathione. We propose that SoxAX cytochromes are a new type of heme-copper proteins, with SoxAX-mediated S-S bond formation involving both the copper and heme centers.