Far- and Mid-Infrared Spectroscopic Analysis of the Substrate-Induced Structural Dynamics of Respiratory Complex I

Authors

  • Dr. Ruth Hielscher,

    1. Institut de Chimie, UMR 7177, Laboratoire de spectroscopie vibrationnelle et électrochimie des biomolécules, CNRS Université de Strasbourg, 1, rue Blaise Pascal, 67070 Strasbourg (France), Fax: (+33) 368 85141
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  • Prof. Dr. Thorsten Friedrich,

    1. Institut für Organische Chemie und Biochemie, Albert-Ludwigs-Universität, Albertstraße 21, 79104 Freiburg (Germany)
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  • Prof. Dr. Petra Hellwig

    Corresponding author
    1. Institut de Chimie, UMR 7177, Laboratoire de spectroscopie vibrationnelle et électrochimie des biomolécules, CNRS Université de Strasbourg, 1, rue Blaise Pascal, 67070 Strasbourg (France), Fax: (+33) 368 85141
    • Institut de Chimie, UMR 7177, Laboratoire de spectroscopie vibrationnelle et électrochimie des biomolécules, CNRS Université de Strasbourg, 1, rue Blaise Pascal, 67070 Strasbourg (France), Fax: (+33) 368 85141
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Abstract

The catalytic activity of the respiratory NADH:ubiquinone oxidoreductase (complex I) is based on conformational reorganizations. Herein we probe the effect of substrates on the conformational flexibility of complex I by means of 1H/2H exchange kinetics at the level of the amide proton in the mid-infrared spectral range (1700–1500 cm−1). Slow, medium, and fast exchanging domains are distinguished that reveal different accessibilities to the solvent. Whereas amide hydrogens undergo rapid exchange with the solvent in an open structure, hydrogens experience much slower exchange when they are involved in H-bonded structures or when they are sterically inaccessible for the solvent. The results indicate a structure that is more open in the presence of both NADH and quinon. Complementary information on the overall internal hydrogen bonding of the protein was probed in the far infrared (300–30 cm−1), a spectral range that includes a continuum mode of the hydrogen bonding signature.

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