A Self-Assembled Respiratory Chain that Catalyzes NADH Oxidation by Ubiquinone-10 Cycling between ComplexI and the Alternative Oxidase

ComplexI is a crucial respiratory enzyme that conserves the energy from NADH oxidation by ubiquinone-10 (Q10) in proton transport across a membrane. Studies of its energy transduction mechanism are hindered by the extreme hydrophobicity of Q10, and they have so far relied on native membranes with ma...

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Bibliographic Details
Published in:Angewandte Chemie 2016-01, Vol.128 (2), p.738-741
Main Authors: Jones, Andrew J Y, Blaza, James N, Bridges, Hannah R, May, Benjamin, Moore, Anthony L, Hirst, Judy
Format: Article
Language:eng ; ger
Subjects:
Agrochemicals
Alternative oxidase
Bicycles
Catalysis
Chains
Chemistry
Coenzyme Q10
Cycles
Electron transport
Energy conservation
Energy transduction
Enzymes
Fungicides
Hydrophobicity
Hydroquinone
Inhibitors
Mammals
Membranes
NADH
Nicotinamide adenine dinucleotide
Oxidase
Oxidation
Pesticides
Pharmaceuticals
Quinol oxidase
Quinones
Side reactions
Transport
Ubiquinone
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Summary:ComplexI is a crucial respiratory enzyme that conserves the energy from NADH oxidation by ubiquinone-10 (Q10) in proton transport across a membrane. Studies of its energy transduction mechanism are hindered by the extreme hydrophobicity of Q10, and they have so far relied on native membranes with many components or on hydrophilic Q10 analogues that partition into membranes and undergo side reactions. Herein, we present a self-assembled system without these limitations: proteoliposomes containing mammalian complexI, Q10, and a quinol oxidase (the alternative oxidase, AOX) to recycle Q10H2 to Q10. AOX is present in excess, so complexI is completely rate determining and the Q10 pool is kept oxidized under steady-state catalysis. The system was used to measure a fully-defined KM value for Q10. The strategy is suitable for any enzyme with a hydrophobic quinone/quinol substrate, and could be used to characterize hydrophobic inhibitors with potential applications as pharmaceuticals, pesticides, or fungicides.
ISSN:0044-8249
1521-3757
DOI:10.1002/ange.201507332