The amitochondriate eukaryote Trichomonas vaginalis contains a divergent thioredoxin-linked peroxiredoxin antioxidant system (2004)

Author(s): Coombs GH, Westrop GD, Suchan P, Puzova G, Hirt RP, Embley TM, Mottram JC, Muller S

    Abstract: Trichomonas is an amitochondriate parasitic protozoon specialized for an anaerobic lifestyle. Nevertheless, it is exposed to oxygen and is able to cope with the resultant oxidative stress. In the absence of glutathione, cysteine has been thought to be the major antioxidant. We now report that the parasite contains thioredoxin reductase, which functions together with thioredoxin and thioredoxin peroxidase to detoxify potentially damaging oxidants. Thioredoxin reductase and thioredoxin also reduce cystine and so may play a role in maintaining the cellular cysteine levels. The importance of the thioredoxin system as one of the major antioxidant defense mechanisms in Trichomonas was confirmed by showing that the parasite responds to environmental changes resulting in increased oxidative stress by up-regulating thioredoxin and thioredoxin peroxidases levels. Sequence data indicate that the thioredoxin reductase of Trichomonas differs fundamentally in structure from that of its human host and thus may represent a useful drug target. The protein is generally similar to thioredoxin reductases present in other lower eukaryotes, all of which probably originated through horizontal gene transfer from a prokaryote. The phylogenetic signal in thioredoxin peroxidase is weak, but evidence from trees suggests that this gene has been subject to repeated horizontal gene transfers from different prokaryotes to different eukaryotes. The data are thus consistent with the complexity hypothesis that predicts that the evolution of simple pathways such as the thioredoxin cascade are likely to be affected by horizontal gene transfer between species.

      • Date: 13-02-2004
      • Journal: Journal of Biological Chemistry
      • Volume: 279
      • Issue: 7
      • Pages: 5249-5256
      • Publisher: American Society for Biochemistry and Molecular Biology, Inc.
      • Publication type: Article
      • Bibliographic status: Published

      Keywords: Amino Acid Sequence Animals Antioxidants/chemistry Blotting, Northern Blotting, Western Cloning, Molecular Cysteine/chemistry Electrophoresis, Polyacrylamide Gel Gene Transfer Techniques Glutathione/metabolism Kinetics Molecular Sequence Data Oxidation-Reduction Oxidative Stress Oxygen/metabolism Peroxidases/*chemistry Phylogeny RNA, Messenger/metabolism Recombinant Proteins/metabolism Research Support, Non-U.S. Gov't Sequence Homology, Amino Acid Species Specificity Thioredoxin/*chemistry Thioredoxin Reductase (NADPH)/chemistry Time Factors Trichomonas vaginalis/*metabolism


      Professor Robert Hirt
      Professor of Evolutionary Parasitology