Multiple Q-Cycle Bypass Reactions at the Qo Site of the Cytochiome bc(1) Complex

Journal Article · Sat May 25 04:00:00 EDT 2002 · Biochemistry

DOI:https://doi.org/10.1021/bi025581e· OSTI ID:889572

Muller, Florian L; Crofts, Antony R; Kramer, David M

The cytochrome (cyt) bc1 complex is central to energy transduction in many species. Most investigators now accept a modified Q-cycle as the catalytic mechanism of this enzyme. Several thermodynamically favorable side reactions must be minimized for efficient functioning of the Q-cycle. Among these, reduction of oxygen by the Qo site semiquinone to produce superoxide is of special pathobiological interest. These superoxide-producing bypass reactions are most notably observed as the antimycin A- or myxothiazol-resistant reduction of cyt c. In this work, we demonstrate that these inhibitor resistant cyt c reductase activities are largely unaffected by removal of O2 in the isolated yeast cyt bc1 complex. Further, increasing O2 tension 5-fold stimulated the antimycin A-resistant reduction by a small amount (25%), while leaving the myxothiazol-resistant reduction unchanged.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 889572
• Journal Information: Biochemistry, Journal Name: Biochemistry Journal Issue: 25 Vol. 41
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
60 APPLIED LIFE SCIENCES
ANTIBIOTICS
CYTOCHROMES
Environmental Molecular Sciences Laboratory
OXIDOREDUCTASES
OXYGEN
REMOVAL
YEASTS