Department of Botany, King's College, University of London, 68 Half Moon Lane, London S.E. 24., Great Britain
Abstract:
A procedure is described for preparing particles from cells of Micrococcus denitrificans which were broken osmotically after treatment with lysozyme.
1. 1. The preparations catalysed ATP synthesis coupled to O2 uptake or NO3? reduction. With NADH or succinate as the electron donors the P:O ratios were about 1.5 and 0.5, respectively; and the P:NO3? ratios were about 0.9 and 0.06, respectively.
2. 2. Addition of ADP or Pi to the reaction mixture increased the rates of NADH-dependent O2 uptake and NO3? reduction. Addition of 1 mM 2,4-dinitrophenol, which inhibited phosphorylation by 50–60%, increased the basal rates of electron transport.
3. 3. Evidence derived from spectrophotometry and from the differential inhibition by antimycin A of O2 and NO3? reduction leads to the conclusion that the nitrate reductase interacted with the respiratory chain in the region of the b-type cytochrome, and that the c-type cytochrome present was not involved in the reduction of NO3? to NO2?.