Microsporidia are highly specialized obligate intracellular parasites of other eukaryotes (including humans1) that show extreme reduction at the molecular, cellular and biochemical level2,3. Although microsporidia have long been considered as early branching eukaryotes that lack mitochondria4, they have recently been shown to contain a tiny mitochondrial remnant called a mitosome2,5. The function of the mitosome is unknown, because microsporidians lack the genes for canonical mitochondrial functions, such as aerobic respiration and haem biosynthesis. However, microsporidial genomes encode several components of the mitochondrial iron–sulphur (Fe–S) cluster assembly machinery. Here we provide experimental insights into the metabolic function and localization of these proteins. We cloned, functionally characterized and localized homologues of several central mitochondrial Fe–S cluster assembly components for the microsporidians Encephalitozoon cuniculi and Trachipleistophora hominis. Several microsporidial proteins can functionally replace their yeast counterparts in Fe–S protein biogenesis. In E. cuniculi, the iron (frataxin) and sulphur (cysteine desulphurase, Nfs1) donors and the scaffold protein (Isu1) co-localize with mitochondrial Hsp70 to the mitosome, consistent with it being the functional site for Fe–S cluster biosynthesis. In T. hominis, mitochondrial Hsp70 and the essential sulphur donor (Nfs1) are still in the mitosome, but surprisingly the main pools of Isu1 and frataxin are cytosolic, creating a conundrum of how these key components of Fe–S cluster biosynthesis coordinate their function. Together, our studies identify the essential biosynthetic process of Fe–S protein assembly as a key function of microsporidian mitosomes.
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Keeling, P. J. & Fast, N. M. Microsporidia: biology and evolution of highly reduced intracellular parasites. Annu. Rev. Microbiol. 56, 93–116 (2002)
Katinka, M. D. et al. Genome sequence and gene compaction of the eukaryote parasite Encephalitozoon cuniculi . Nature 414, 450–453 (2001)
Burri, L., Williams, B. A., Bursac, D., Lithgow, T. & Keeling, P. J. Microsporidian mitosomes retain elements of the general mitochondrial targeting system. Proc. Natl Acad. Sci. USA 103, 15916–15920 (2006)
Embley, T. M. & Martin, W. Eukaryotic evolution, changes and challenges. Nature 440, 623–630 (2006)
Williams, B. A., Hirt, R. P., Lucocq, J. M. & Embley, T. M. A mitochondrial remnant in the microsporidian Trachipleistophora hominis . Nature 418, 865–869 (2002)
Lill, R. & Kispal, G. Maturation of cellular Fe-S proteins: an essential function of mitochondria. Trends Biochem. Sci. 25, 352–356 (2000)
Kispal, G. et al. Biogenesis of cytosolic ribosomes requires the essential iron-sulphur protein Rli1p and mitochondria. EMBO J. 24, 589–598 (2005)
Wiedemann, N. et al. Essential role of Isd11 in mitochondrial iron-sulfur cluster synthesis on Isu scaffold proteins. EMBO J. 25, 184–195 (2006)
Lill, R. & Muhlenhoff, U. Iron-sulfur protein biogenesis in eukaryotes: components and mechanisms. Annu. Rev. Cell Dev. Biol. 22, 457–486 (2006)
Emelyanov, V. V. Phylogenetic affinity of a Giardia lamblia cysteine desulfurase conforms to canonical pattern of mitochondrial ancestry. FEMS Microbiol. Lett. 226, 257–266 (2003)
Tovar, J. et al. Mitochondrial remnant organelles of Giardia function in iron-sulphur protein maturation. Nature 426, 172–176 (2003)
Molik, S., Lill, R. & Muhlenhoff, U. Methods for studying iron metabolism in yeast mitochondria. Methods Cell Biol. 80, 261–280 (2007)
Guda, C., Fahy, E. & Subramaniam, S. MITOPRED: a genome-scale method for prediction of nucleus-encoded mitochondrial proteins. Bioinformatics 20, 1785–1794 (2004)
Gerber, J., Neumann, K., Prohl, C., Muhlenhoff, U. & Lill, R. The yeast scaffold proteins Isu1p and Isu2p are required inside mitochondria for maturation of cytosolic Fe–S proteins. Mol. Cell. Biol. 24, 4848–4857 (2004)
Muhlenhoff, U., Gerber, J., Richhardt, N. & Lill, R. Components involved in assembly and dislocation of iron-sulfur clusters on the scaffold protein Isu1p. EMBO J. 22, 4815–4825 (2003)
Dutkiewicz, R. et al. The Hsp70 chaperone Ssq1p is dispensable for iron-sulfur cluster formation on the scaffold protein Isu1p. J. Biol. Chem. 281, 7801–7808 (2006)
Netz, D. J., Pierik, A. J., Stumpfig, M., Muhlenhoff, U. & Lill, R. The Cfd1-Nbp35 complex acts as a scaffold for iron-sulfur protein assembly in the yeast cytosol. Nature Chem. Biol. 3, 278–286 (2007)
Abrahamsen, M. S. et al. Complete genome sequence of the apicomplexan, Cryptosporidium parvum . Science 304, 441–445 (2004)
Loftus, B. et al. The genome of the protist parasite Entamoeba histolytica . Nature 433, 865–868 (2005)
Carlton, J. M. et al. Draft genome sequence of the sexually transmitted pathogen Trichomonas vaginalis . Science 315, 207–212 (2007)
Ali, V., Shigeta, Y., Tokumoto, U., Takahashi, Y. & Nozaki, T. An intestinal parasitic protist, Entamoeba histolytica, possesses a non-redundant nitrogen fixation-like system for iron-sulfur cluster assembly under anaerobic conditions. J. Biol. Chem. 279, 16863–16874 (2004)
Johnson, D. C., Dean, D. R., Smith, A. D. & Johnson, M. K. Structure, function, and formation of biological iron-sulfur clusters. Annu. Rev. Biochem. 74, 247–281 (2005)
Rouault, T. A. & Tong, W. H. Iron-sulphur cluster biogenesis and mitochondrial iron homeostasis. Nature Rev. Mol. Cell Biol. 6, 345–351 (2005)
Balk, J. & Lobreaux, S. Biogenesis of iron-sulfur proteins in plants. Trends Plant Sci. 10, 324–331 (2005)
Sutak, R. et al. Mitochondrial-type assembly of FeS centers in the hydrogenosomes of the amitochondriate eukaryote Trichomonas vaginalis . Proc. Natl Acad. Sci. USA 101, 10368–10373 (2004)
Vavra, J. “Polar vesicles” of microsporidia are mitochondrial remnants (“mitosomes”)? Folia Parasitol. (Praha) 52, 193–195 (2005)
Muhlenhoff, U. et al. Functional characterization of the eukaryotic cysteine desulfurase Nfs1p from Saccharomyces cerevisiae . J. Biol. Chem. 279, 36906–36915 (2004)
Muhlenhoff, U., Richhardt, N., Ristow, M., Kispal, G. & Lill, R. The yeast frataxin homolog Yfh1p plays a specific role in the maturation of cellular Fe–S proteins. Hum. Mol. Genet. 11, 2025–2036 (2002)
Mumberg, D., Muller, R. & Funk, M. Yeast vectors for the controlled expression of heterologous proteins in different genetic backgrounds. Gene 156, 119–122 (1995)
Taupin, V., Metenier, G., Vivares, C. P. & Prensier, G. An improved procedure for percoll gradient separation of sporogonial stages in Encephalitozoon cuniculi (Microsporidia). Parasitol. Res. 99, 708–714 (2006)
A.V.G. acknowledges the support of a Marie Curie Fellowship from the European Commission and T.M.E. acknowledges support from the British Royal Society and the Leverhulme Trust. We thank A. J. Pierik and C. Noel for help in identifying ThIsd11;, J. Ihrig and B. Keys for experimental support; and T. Booth for help with confocal microscopy. R.L. acknowledges support from Deutsche Forschungsgemeinschaft (Gottfried-Wilhelm Leibniz program and SFB-TR1), European Commission (MitEURO), and Fonds der Chemischen Industrie.
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Goldberg, A., Molik, S., Tsaousis, A. et al. Localization and functionality of microsporidian iron–sulphur cluster assembly proteins. Nature 452, 624–628 (2008). https://doi.org/10.1038/nature06606
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