Bacterial-type oxygen detoxification and iron-sulfur cluster assembly in amoebal relict mitochondria.
van der Giezen, M
The assembly of vital reactive iron-sulfur (Fe-S) cofactors in eukaryotes is mediated by proteins inherited from the original mitochondrial endosymbiont. Uniquely among eukaryotes, however, Entamoeba and Mastigamoeba lack such mitochondrial-type Fe-S cluster assembly proteins and possess instead an analogous bacterial-type system acquired by lateral gene transfer. Here we demonstrate, using immunomicroscopy and biochemical methods, that beyond their predicted cytosolic distribution the bacterial-type Fe-S cluster assembly proteins NifS and NifU have been recruited to function within the relict mitochondrial organelles (mitosomes) of Entamoeba histolytica. Both Nif proteins are 10-fold more concentrated within mitosomes compared with their cytosolic distribution suggesting that active Fe-S protein maturation occurs in these organelles. Quantitative immunoelectron microscopy showed that amoebal mitosomes are minute but highly abundant cellular structures that occupy up to 2% of the total cell volume. In addition, protein colocalization studies allowed identification of the amoebal hydroperoxide detoxification enzyme rubrerythrin as a mitosomal protein. This protein contains functional Fe-S centres and exhibits peroxidase activity in vitro. Our findings demonstrate the role of analogous protein replacement in mitochondrial organelle evolution and suggest that the relict mitochondrial organelles of Entamoeba are important sites of metabolic activity that function in Fe-S protein-mediated oxygen detoxification.
addresses: School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK.
types: Journal Article; Research Support, Non-U.S. Gov't
Online open article. This is a copy of an article published in Cellular Microbiology © 2009 Blackwell Publishing Ltd. Cellular Microbiology is available online at: http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1462-5822
Cellular Microbiology , 2010, Vol. 12, Issue 3, pp. 331 - 342
Place of publication