Complex I: a chimaera of a redox and conformation-driven proton pump?
From phylogenetic sequence analysis, it can be concluded that the proton-pumping NADH:ubiquinone oxidoreductase (complex I) has evolved from preexisting modules for electron transfer and proton translocation. It is built up by a peripheral NADH dehydrogenase module, an amphipatic hydrogenase module, and a membrane-bound transporter module. These modules, or at least part of them, are also present in various other bacterial enzymes. It is assumed that they fulfill a similar function in complex I and related enzymes. Based on the function of the individual modules, it is possible to speculate about the mechanism of complex I. The hydrogenase module might work as a redox-driven proton pump, while the transporter module might act as a conformation-driven proton pump. This implies that complex I contains two energy-coupling sites. The NADH dehydrogenase module seems to be involved in electron transfer and not in proton translocation.
Friedrich
T
T
Institut für Biochemie, Universität Düsseldorf, Germany. Thorsten.Friedrich@uni-duesseldorf.de
D042967:Electron Transport Complex I; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D019143:Evolution, Molecular; D008958:Models, Molecular; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010084:Oxidation-Reduction; D011487:Protein Conformation; D017494:Proton Pumps / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D017494:Proton Pumps; D011993:Recombinant Fusion Proteins; D009247:NADH, NADPH Oxidoreductases; D042967:Electron Transport Complex I