An electrogenic redox loop in sulfate reduction reveals a likely widespread mechanism of energy conservation

• DOI: 10.1038/s41467-018-07839-x
• Publication Date: 2018-12-17T16:55:17Z
• Authors: Américo G. Duarte; Teresa Catarino; Gaye F. White; Diana Lousa; Sinje Neukirchen; Cláudio M. Soares; Filipa L. Sousa; Thomas A. Clarke; Inês A. C. Pereira
• Keywords: 0301 basic medicine; Science; 106002 Biochemie; Cell Respiration; PROTEIN; HYDROGENASE; SDG 7 – Bezahlbare und saubere Energie; OXIDATION; 7. Clean energy; Article; Membrane Potentials; 03 medical and health sciences; RELEVANCE; SDG 7 - Affordable and Clean Energy; Anaerobiosis; Desulfovibrio vulgaris; COMPLEX; IDENTIFICATION; Bioenergetics, Biophysical methods; Sulfates; Q; 500; Bacteriology; 106002 Biochemistry; Vitamin K 2; BIOENERGETICS; TRANSPORT; RECONSTITUTION; RESPIRATION; Electron Transport Chain Complex Proteins; Metabolic pathways; Enzyme mechanisms; Liposomes; Protons; Energy Metabolism; Oxidation-Reduction

AbstractThe bioenergetics of anaerobic metabolism frequently relies on redox loops performed by membrane complexes with substrate- and quinone-binding sites on opposite sides of the membrane. However, in sulfate respiration (a key process in the biogeochemical sulfur cycle), the substrate- and quinone-binding sites of the QrcABCD complex are periplasmic, and their role in energy conservation has not been elucidated. Here we show that the QrcABCD complex of Desulfovibrio vulgaris is electrogenic, as protons and electrons required for quinone reduction are extracted from opposite sides of the membrane, with a H+/e− ratio of 1. Although the complex does not act as a H+-pump, QrcD may include a conserved proton channel leading from the N-side to the P-side menaquinone pocket. Our work provides evidence of how energy is conserved during dissimilatory sulfate reduction, and suggests mechanisms behind the functions of related bacterial respiratory complexes in other bioenergetic contexts.