Journal
EUROPEAN JOURNAL OF BIOCHEMISTRY
Volume 269, Issue 16, Pages 4020-4024Publisher
BLACKWELL PUBLISHING LTD
DOI: 10.1046/j.1432-1033.2002.03091.x
Keywords
NADH : Q oxidoreductase; complex I; reverse electron transfer; Paracoccus denitrificans; rotenone
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Tightly coupled inside-out vesicles were prepared from Paracoccus denitrificans cells (SPP, sub-Paracoccus particles) and characterized kinetically. The rate of NADH oxidation, catalysed by SPP, increases 6-8 times on addition of gramicidin. The vesicles are capable of catalysing DeltamuH(+)-dependent reverse electron transfer from quinol to NAD(+) The kinetic parameters of the NADH-oxidase and the reverse electron transfer carried out by membrane-bound P. denitrificans complex I were estimated and compared with those of the mitochondrial enzyme. The data demonstrate that catalytic properties of the dinucleotide-binding site of the bacterial and mitochondrial complex I are almost identical, pointing out similar organization of the site in mammals and P. denitrificans. Inhibition of the bacterial complex I by a specific inhibitor of Q reduction, rotenone, is very different from that of the mitochondrial enzyme. The inhibitor is capable of suppressing the NADH oxidation reaction only at micromolar concentrations, while the activity of mitochondrial enzyme is suppressed by nano-molar concentrations of rotenone. In contrast to the mitochondrial enzyme, rotenone, even at concentrations as high as 10 muM, does not inhibit the reverse, DeltamuH(+)-dependent NAD(+)-reductase reaction on SPP.
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