Bacterial NADH-quinone oxidoreductases: Iron-sulfur clusters and related problems

Abstract

Many bacteria contain proton-translocating membrane-bound NADH-quinone oxidoreductases (NDH-1), which demonstrate significant genetic, spectral, and kinetic similarity with their mitochondrial counterparts. This review is devoted to the comparative aspects of the iron-sulfur cluster composition of NDH-1 from the most well-studied bacterial systems to date.: Paracoccus denitrificans, Rhodobacter sphaeroides, Escherichia coli, and Thermus thermophilus. These bacterial systems provide useful models for the study of coupling Site I and contain all the essential parts of the electron-transfer and proton-translocating machinery of their eukaryotic counterparts.

Genetic inactivation of the H+‐translocating NADH:ubiquinone oxidoreductase of Paracoccus denitrificans is facilitated by insertion of the ndh gene from Escherichia coli

“…Despite having about half the molecular mass of complex I and a third of its subunits, the P. denitrificans NDH1 contains the same set of redox centres [6,7]. Furthermore, the EPR spectra of all the detectable Fe-S clusters in P. denitrificans NDH1, unlike those of E. coli, are very similar to the respective clusters in complex I [5][6][7][8].…”

Studies on the proton‐translocating NADH:ubiquinone oxidoreductases of mitochondria and Escherichia coli using the inhibitor 1,10‐phenanthroline

“…However, in a recent study on the isolated enzyme, three different binuclear clusters were reported [6]. One of them, Nla, has a very low midpoint potential and is thus expected to be EPRinvisible under the conditions used here.…”

“…The second one was named N 1 b (gX,Y.Z = 1.94, 1.94, 2.03), due to its similarity to the mitochondrial cluster 1 b. The third binucfear cluster, named Nlc &X,Y,Z = 1.92, 1.95, 1.99>, is unique to E. coZi NDHl and no homologous cluster is currently known in any other enzyme of this family [6]. change during long incubation [5].…”

“…4) were recorded from such membranes incubated in the presence of OP together with either NADH, or succinate, or both. Spectroscopy was carried out under different conditions of temperature and radiation power, in order to detect both slow and fast relaxing clusters, as well as to allow direct comparison to the spectra in [6]. The EPR spectrum of NADH-redu~d membranes at 40 K indicates the presence of at least one slow-relaxing Fe-S cluster (Fig.…”

“…On the other hand, the enzyme from E. coli is much less similar to complex I in such properties [2,5,6]. In contrast to the large difference in their rotenone sensitivity, the inhibition of both Paracoccus and E. coli NDHl by capsaicin is nearly identical [7].…”