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

Lowe, Elisabeth C.; Bydder, Sarah; Hartshorne, Robert S.; Tape, Hannah L. U.; Dridge, Elizabeth J.; Debieux, Charles M.; Paszkiewicz, Konrad; Singleton, Ian; Lewis, Richard J.; Santini, Joanne M.; Richardson, David J.; Butler, Clive S.

Abstract

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

Citation

Lowe, E. C., Bydder, S., Hartshorne, R. S., Tape, H. L. U., Dridge, E. J., Debieux, C. M., Paszkiewicz, K., Singleton, I., Lewis, R. J., Santini, J. M., Richardson, D. J., & Butler, C. S. (2010). Quinol-cytochrome c Oxidoreductase and Cytochrome c4 Mediate Electron Transfer during Selenate Respiration in Thauera selenatis. Journal of Biological Chemistry, 285(24), 18433-18442. https://doi.org/10.1074/jbc.M110.115873

• Journal Article Type: Article
• Online Publication Date: Apr 13, 2010
• Publication Date: Jun 11, 2010
• Deposit Date: Aug 2, 2016
• Journal: Journal of Biological Chemistry
• Print ISSN: 0021-9258
• Electronic ISSN: 1083-351X
• Publisher: American Society for Biochemistry and Molecular Biology
• Peer Reviewed: Peer Reviewed
• Volume: 285
• Issue: 24
• Pages: 18433-18442
• DOI: https://doi.org/10.1074/jbc.M110.115873
• Keywords: Cell Biology; Biochemistry; Molecular Biology
• Public URL: http://researchrepository.napier.ac.uk/Output/322411