Oxidoreduction properties of bound ubiquinone in Complex I from Escherichia coli.
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013;
1837:246-50. [PMID:
24216024 DOI:
10.1016/j.bbabio.2013.11.001]
[Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Revised: 10/31/2013] [Accepted: 11/04/2013] [Indexed: 12/12/2022]
Abstract
The exploration of the redox chemistry of bound ubiquinone during catalysis is a prerequisite for the understanding of the mechanism by which Complex I (nicotinamide adenine dinucleotide (NADH):ubiquinone oxidoreductase) transduces redox energy into an electrochemical proton gradient. Studies of redox dependent changes in the spectrum of Complex I from Escherichia coli in the mid- and near-ultraviolet (UV) and visible areas were performed to identify the spectral contribution, and to determine the redox properties, of the tightly bound ubiquinone. A very low midpoint redox potential (<-300mV) was found for the bound ubiquinone, more than 400mV lower than when dissolved in a phospholipid membrane. This thermodynamic property of bound ubiquinone has important implications for the mechanism by which Complex I catalyzes proton translocation.
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