Reductive inactivation of the mitochondrial three subunit NADH dehydrogenase.
The 3-subunit iron-sulfur flavoprotein (NADH-artificial electron acceptor oxidoreductase) derived from complex I (EC 1.6.5.3) is rapidly and irreversibly inactivated in the presence of NADH. The rate of inactivation increases with a decrease of the enzyme concentration. The activities with ferricyanide, menadione and cytochrome c were lost synchronously during preincubation of the enzyme in the presence of NADH or dithionite under either aerobic or anaerobic conditions. The titration of the inactivation rate with the NADH/NAD+ pair suggests that reduction of a component with Em' = -325 mV (n = 2) is a prerequisite for a loss of the enzyme activity. Among the compounds tested only FMN and NAD+ were able to protect the enzyme against the reductive inactivation. NADH-induced loss of the enzyme activity in diluted solutions is accompanied with the synchronous appearance of a fluorescence characteristic for free FMN. It is concluded that the reduction of flavin leads to a strong decrease of FMN affinity to its specific binding site, and possible implications of the redox-dependent affinity changes in operation of NADH-ubiquinone reductase are discussed.
Sled
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VD
Department of Biochemistry, School of Biology, Moscow State University, Russia.
Vinogradov
A D
AD
D003574:Cytochrome c Group; D004227:Dithionite; D042967:Electron Transport Complex I; D005292:Ferricyanides; D005486:Flavin Mononucleotide; D009245:NADH Dehydrogenase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism*; D010084:Oxidation-Reduction; D011487:Protein Conformation; D014812:Vitamin K
D003574:Cytochrome c Group; D005292:Ferricyanides; D014812:Vitamin K; C007931:hexacyanoferrate III; D004227:Dithionite; D005486:Flavin Mononucleotide; D009247:NADH, NADPH Oxidoreductases; D009245:NADH Dehydrogenase; D042967:Electron Transport Complex I