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Proton-coupled electron transfer dynamics in the alternative oxidase.

Patricia Saura1, Hyunho Kim1, Adel Beghiah1

  • 1Department of Biochemistry and Biophysics, Stockholm University Stockholm 10691 Sweden ville.kaila@dbb.su.se.

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|October 24, 2024
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Summary
This summary is machine-generated.

Alternative oxidase (AOX) uses a water-mediated proton-coupled electron transfer to split oxygen, generating a tyrosyl radical that oxidizes quinol. Conserved carboxylates facilitate this crucial catalytic process in parasites.

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Area of Science:

  • Biochemistry
  • Structural Biology
  • Computational Biology

Background:

  • Alternative oxidase (AOX) is a key enzyme in respiratory chains of various organisms, including pathogens.
  • Despite extensive research, the precise catalytic mechanism of AOX remains elusive.
  • Understanding AOX is crucial for developing drugs against parasitic diseases.

Purpose of the Study:

  • To elucidate the proton-coupled electron transfer (PCET) mechanism of AOX from *Trypanosoma brucei*.
  • To investigate the role of specific amino acid residues in AOX catalysis.
  • To provide a molecular basis for rational drug design targeting parasitic AOX.

Main Methods:

  • Multi-scale quantum and classical molecular simulations.
  • Biochemical experiments, including site-directed mutagenesis.
  • Analysis of proton-coupled electron transfer reactions.

Main Results:

  • AOX activates and splits dioxygen via a water-mediated PCET reaction.
  • A high-valent ferryl/ferric species and a tyrosyl radical (Tyr220˙) are key intermediates.
  • Conserved carboxylates (Glu215, Asp100) function as transient proton-loading sites, confirmed by mutagenesis.
  • Electric field effects mediated by ion-paired networks are critical for catalysis.

Conclusions:

  • The study reveals a detailed mechanism for AOX catalysis involving water-mediated PCET and electric field effects.
  • Identified conserved carboxylates are essential for quinol oxidation.
  • Findings offer a molecular foundation for developing novel antiparasitic drugs targeting AOX.