title: Anaerobic respiration and energy conservation in Paracoccus denitrificans. Functioning of iron-sulfur centers and the uncoupling effect of nitrite.
abstract: 1. Electron paramagnetic resonance spectra at 8-60 K of NADH-reduced membrane particles prepared from Paracoccus denitrificans grown anaerobically with nitrate as terminal electron acceptor show the presence of iron-sulfur centers 1-4 in the NADH-ubiquinone segment of the respiratory chain. In addition resonance lines at g = 2.058, g = 1.953 and g = 1.88 are detectable in the spectra of succinate-reduced membranes at 15 K, which are attributed to the iron-sulfur-containing nitrate reductase. 2. Sulphate-limited growth under anaerobic conditions does not affect the iron-sulfur pattern of NADH dehydrogenase or nitrate reductase. Furthermore respiratory chain-linked electron transport and its inhibition by rotenone are not influenced. These results contrast those observed for sulphate-limited growth of P. denitrificans under aerobic conditions [Eur. J. Biochem. (1977) 81, 267-275]. 3. Proton translocation studies of whole cells indicate that nitrite increases the proton conductance of the cytoplasmic membrane, resulting in a collapse of the proton gradient across the membrane. Nitrite accumulates under anaerobic growth conditions with nitrate as terminal electron acceptor; the extent of accumulation depends on the specific growth conditions. Thus the low efficiencies of respiratory chain-linked energy conservation observed during nitrate respiration [Arch. Microbiol. (1977) 112, 17-23] can be explained by the uncoupling action of nitrite.
mesh_terms: D000693:Anaerobiosis; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D007506:Iron-Sulfur Proteins / Q000378:metabolism*; D007700:Kinetics; D008667:Metalloproteins / Q000378:metabolism*; D009573:Nitrites / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects; D010230:Paracoccus / Q000187:drug effects / Q000378:metabolism*; D014475:Uncoupling Agents
chemical_list: D007506:Iron-Sulfur Proteins; D008667:Metalloproteins; D009573:Nitrites; D014475:Uncoupling Agents