| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1942436 | Biochimica et Biophysica Acta (BBA) - Bioenergetics | 2012 | 9 Pages |
The proton-pumping NADH:ubiquinone oxidoreductase, respiratory complex I, couples the electron transfer from NADH to ubiquinone with the translocation of protons across the membrane. In Escherichia coli the complex is made up of 13 different subunits encoded by the so-called nuo-genes. Mutants, in which each of the nuo-genes was individually disrupted by the insertion of a resistance cartridge were unable to assemble a functional complex I. Each disruption resulted in the loss of complex I-mediated activity and the failure to extract a structurally intact complex. Thus, all nuo-genes are required either for the assembly or the stability of a functional E. coli complex I. The three subunits comprising the soluble NADH dehydrogenase fragment of the complex were detected in the cytoplasm of several nuo-mutants as one distinct band after BN-PAGE. It is discussed that the fully assembled NADH dehydrogenase fragment represents an assembly intermediate of the E. coli complex I. A partially assembled complex I bound to the membrane was detected in the nuoK and nuoL mutants, respectively. Overproduction of the ΔNuoL variant resulted in the accumulation of two populations of a partially assembled complex in the cytoplasmic membranes. Both populations are devoid of NuoL. One population is enzymatically active, while the other is not. The inactive population is missing cluster N2 and is tightly associated with the inducible lysine decarboxylase. This article is part of a Special Issue entitled: Biogenesis/Assembly of Respiratory Enzyme Complexes.
► Respiratory complex I from E. coli consists of 13 subunits. ► All corresponding genes are essential for the assembly of the complex. ► A soluble fragment of the complex is accumulated in various complex I mutants. ► A membranous fragment accumulates in the ΔnuoL and ΔnuoK mutants. ► Overproduction leads to a variant associated with inducible lysine decarboxylase.
