Modulation of the active site conformation by site-directed mutagenesis in cytochrome c oxidase from Paracoccus denitrificans

Hong Ji, Tapan K. Das, Anne Puustinen, Mårten Wikström, Syun Ru Yeh, Denis L. Rousseau

Research output: Contribution to journalArticle

7 Scopus citations

Abstract

The structural and functional properties of active site mutants of cytochrome c oxidase from Paracoccus denitrificans (PdCcO) were investigated with resonance Raman spectroscopy. Based on the Fe-CO stretching modes and low frequency heme modes, two conformers (α- and β-forms) were identified that are in equilibrium in the enzyme. The α-conformer, which is the dominant species in the wild-type enzyme, has a shorter heme a3 iron-CuB distance and a more distorted heme, as compared to the β-conformer, which has a more relaxed and open distal pocket. In general, the mutations caused a decrease in the population of the α-conformer, which is concomitant with a decreased in the catalytic activity, indicating that the α-conformer is the active form of the enzyme. The data suggest that the native structure of the enzyme is in a delicate balance of intramolecular interactions. We present a model in which the mutations destabilize the α-conformer, with respect to the β-conformer, and raise the activation barrier for the inter-conversion between the two conformers. The accessibility of the two conformers in the conformational space of CcO plausibly plays a critical role in coupling the redox reaction to proton translocation during the catalytic cycle of the enzyme.

Original languageEnglish (US)
Pages (from-to)318-323
Number of pages6
JournalJournal of Inorganic Biochemistry
Volume104
Issue number3
DOIs
StatePublished - Mar 1 2010

Keywords

  • Bioenergetics
  • Cytochrome oxidase
  • Proton translocation
  • Raman scattering

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry

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