Quinol-cytochrome c Oxidoreductase and Cytochrome c4 Mediate Electron Transfer during Selenate Respiration in Thauera selenatis

• DOI: 10.1074/jbc.m110.115873
• Publication Date: 2010-04-14T00:54:21Z
• Authors: Elisabeth C. Lowe; Sarah Bydder; Robert S. Hartshorne; Hannah L.U. Tape; Elizabeth J. Dridge; Charles M. Debieux; Konrad Paszkiewicz; Ian Singleton; Richard J. Lewis; Joanne M. Santini; David J. Richardson; Clive S. Butler
• Keywords: Cytochrome C1

Selenate reductase (SER) from Thauera selenatis is a periplasmic enzyme that has been classified as type II molybdoenzyme. The comprises three subunits SerABC, where SerC an unusual b-heme cytochrome. In the present work spectropotentiometric characterization of component and identification redox partners to SER are reported. mid-point potential was determined by optical titration (Em + 234 ± 10 mV). A profile c-type cytochromes expressed in T. under selenate respiring conditions undertaken. Two were purified (∼24 ∼6 kDa), 24-kDa protein (cytc-Ts4) shown donate electrons SerABC vitro. Protein sequence cytc-Ts4 obtained N-terminal sequencing liquid chromatography-tandem mass spectrometry analysis, based upon similarities, assigned member cytochrome c4 family. Redox potentiometry, combined with UV-visible spectroscopy, showed diheme +282 mV, both hemes predicted have His-Met ligation. To identify membrane-bound electron donors cytc-Ts4, growth presence respiratory inhibitors monitored. specific quinol-cytochrome c oxidoreductase (QCR) myxothiazol antimycin partially inhibited respiration, demonstrating some flux via QCR. Electron transfer QCR novel route for DMSO family molybdoenzymes.