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Letters to Nature

Nature 426, 172-176 (13 November 2003) | doi:10.1038/nature01945; Received 7 April 2003; Accepted 22 July 2003

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Mitochondrial remnant organelles of Giardia function in iron-sulphur protein maturation

Jorge Tovar1, Gloria León-Avila1, Lidya B Sánchez2,5, Robert Sutak3, Jan Tachezy3, Mark van der Giezen1, Manuel Hernández1, Miklós Müller2 & John M. Lucocq4

  1. School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
  2. The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA
  3. Department of Parasitology, Faculty of Science, Charles University, 12844 Prague 2, Czech Republic
  4. School of Life Sciences, WTB/MSI complex, University of Dundee, Dundee DD1 5EH, UK
  5. Present address: Public Health Research Institute, Newark, New Jersey 07103, USA

Correspondence to: Jorge Tovar1 Email: j.tovar@rhul.ac.uk
The sequence of GiiscU has been deposited with GenBank under accession number AY040612.

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Giardia intestinalis (syn. lamblia) is one of the most widespread intestinal protozoan pathogens worldwide, causing hundreds of thousands of cases of diarrhoea each year1. Giardia is a member of the diplomonads, often described as an ancient protist group whose primitive nature is suggested by the lack of typical eukaryotic organelles (for example, mitochondria, peroxisomes), the presence of a poorly developed endomembrane system and by their early branching in a number of gene phylogenies1, 2. The discovery of nuclear genes of putative mitochondrial ancestry in Giardia3, 4, 5, 6, 7 and the recent identification of mitochondrial remnant organelles in amitochondrial protists such as Entamoeba histolytica8, 9 and Trachipleistophora hominis10 suggest that the eukaryotic amitochondrial state is not a primitive condition but is rather the result of reductive evolution. Using an in vitro protein reconstitution assay and specific antibodies against IscS and IscU—two mitochondrial marker proteins involved in iron–sulphur cluster biosynthesis—here we demonstrate that Giardia contains mitochondrial remnant organelles (mitosomes) bounded by double membranes that function in iron–sulphur protein maturation. Our results indicate that Giardia is not primitively amitochondrial and that it has retained a functional organelle derived from the original mitochondrial endosymbiont.

  1. School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK
  2. The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA
  3. Department of Parasitology, Faculty of Science, Charles University, 12844 Prague 2, Czech Republic
  4. School of Life Sciences, WTB/MSI complex, University of Dundee, Dundee DD1 5EH, UK
  5. Present address: Public Health Research Institute, Newark, New Jersey 07103, USA

Correspondence to: Jorge Tovar1 Email: j.tovar@rhul.ac.uk
The sequence of GiiscU has been deposited with GenBank under accession number AY040612.