Sulfide oxidation coupled to ATP synthesis in chicken liver mitochondria

Chicken liver mitochondria consumed O-2 at an accelerated rate when supplie d with low concentrations of hydrogen sulfide. Maximum respiration occurred in 10 muM sulfide. and continued more slowly up to concentrations as high as 60 muM Sulfide oxidation was coupled to adenosine triphosphate (ATP) syn thesis, as shown by firefly luciferase luminescence and by measurement of t he mitochondrial membrane electrochemical gradient. Synthesis of ATP requir ed low, steady-state concentrations of sulfide (<5 muM), which were maintai ned by use of a syringe pump. The ratio of consumed O-2 to sulfide changed at low sulfide and O-2 concentrations, indicating alternative metabolic rea ctions and products. In low concentrations of sulfide, presumably most simi lar to physiological, the O-2/sulfide ratio was 0.75. This is the first rep ort of sulfide oxidation linked to ATP synthesis in any organism not specif ically adapted to a sulfide-rich environment. We suggest that this may be a widespread mitochondrial trait, and that it is consistent with the hypothe sis that mitochondria originated from sulfide-oxidizing symbionts. (C) 2001 Elsevier Science Inc. All rights reserved.