Conformational Component in the Coupled Transfer of Multiple Electrons and Protons in a Monomeric Tetraheme Cytochrome

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Abstract

Cell metabolism relies on energy transduction usually performed by complex membrane-spanning proteins that couple different chemical processes, e.g. electron and proton transfer in proton-pumps. There is great interest in determining at the molecular level the structural details that control these energy transduction events, particularly those involving multiple electrons and protons, because tight control is required to avoid the production of dangerous reactive intermediates. Tetraheme cytochrome c3 is a small soluble and monomeric protein that performs a central step in the bioenergetic metabolism of sulfate reducing bacteria, termed "proton-thrusting," linking the oxidation of molecular hydrogen with the reduction of sulfate. The mechanochemical coupling involved in the transfer of multiple electrons and protons in cytochrome c3 from Desulfovibrio desulfuricans ATCC 27774 is described using results derived from the microscopic thermodynamic characterization of the redox and acid-base centers involved, crystallographic studies in the oxidized and reduced states of the cytochrome, and theoretical studies of the redox and acid-base transitions. This proton-assisted two-electron step involves very small, localized structural changes that are sufficient to generate the complex network of functional cooperativities leading to energy transduction, while using molecular mechanisms distinct from those established for other Desulfovibrio sp. cytochromes from the same structural family.

Original languageEnglish
Pages (from-to)44044-44051
Number of pages8
JournalJournal of Biological Chemistry
Volume276
Issue number47
DOIs
Publication statusPublished - 23 Nov 2001

Keywords

  • Proteins
  • Redox reactions
  • Cells
  • Charge transfer
  • Conformations
  • Crystallography
  • Metabolism
  • Molecular structure

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