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A broad distribution of the alternative oxidase in microsporidian parasites

Bryony A P Williams1, Catherine Elliot, Lena Burri

  • 1School of Biosciences, Geoffrey Pope Building, University of Exeter, Exeter, Devon, United Kingdom.

Plos Pathogens
|February 20, 2010
PubMed

Insights

Microsporidia mitosomes may not be fully anaerobic. Researchers found alternative oxidase (AOX) genes in several microsporidian species, suggesting a role in reoxidizing glycolytic reducing equivalents.

Area of Science:

  • * Eukaryotic cellular biology
  • * Parasitology
  • * Mitochondrial research

Background:

  • * Microsporidia are obligate intracellular parasites with highly reduced mitochondria called mitosomes.
  • * Previously, microsporidia and their mitosomes were considered anaerobic.
  • * The Encephalitozoon cuniculi genome lacks key mitochondrial proteins, supporting the anaerobic hypothesis.

Purpose of the Study:

  • * To investigate the potential for aerobic respiration in microsporidian mitosomes.
  • * To identify and characterize alternative oxidase (AOX) genes in microsporidian genomes.
  • * To determine the functionality and physiological role of AOX in microsporidia.

Main Methods:

  • * Genomic analysis to identify AOX genes in various microsporidian species.
  • * Over-expression of AOX genes from A. locustae and T. hominis in E. coli.
  • * Spectrophotometric measurement of AOX activity using ubiquinol-1 (UQ-1) substrate and specific inhibitors.

Main Results:

  • * Alternative oxidase (AOX) genes were identified in several distantly related microsporidian species, but not in E. cuniculi.
  • * Recombinant AOX proteins from A. locustae and T. hominis exhibited cyanide- and antimycin-resistant activity.
  • * The activity was sensitive to ascofuranone, similar to trypanosomal AOX.

Conclusions:

  • * Mitosomes in certain microsporidian lineages may possess a functional AOX, indicating partial aerobic capacity.
  • * Microsporidian AOX likely reoxidizes reducing equivalents from glycolysis, analogous to trypanosomes.
  • * This finding challenges the long-held view of complete anaerobicity in microsporidia and their mitosomes.

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