Analysis of Genes of Mitochondrial Origin in the Genus Entamoeba

Abstract

The amitochondriate protistan parasite Entamoeba histolytica has lost most mitochondrial functions secondarily but has retained a reduced organelle of mitochondrial origin, the mitosome. We here investigate the presence, origins, and expression in other species of Entamoeba of three genes of mitochondrial origin--pyridine nucleotide transhydrogenase and the mitochondrial-type chaperonins cpn60 and hsp70. The genes appear to be present in all species and specifically related, confirming that the E. histolytica mitosomal genes were not acquired recently by lateral transfer from another organism. Detection of expression was not possible in all cases under the culture conditions used, but several genes were induced during recovery from exposure to a heat shock. This includes the transhydrogenase, which to our knowledge has not been shown previously to be a heat-shock protein.

Evolution of macromolecular import pathways in mitochondria, hydrogenosomes and mitosomes

“…This would argue that sequence divergence between the amoebozoa and opisthokonts is not a barrier to detection of components of the mitochondrial import pathway. However, while the related amoeba E. histolytica has mitosomes with clear matrix-located chaperones and Tom40 and Sam50 proteins to serve in a TOM and SAM complex, further import machinery was not detectable (Tovar et al 1999;Bakatselou et al 2003;Tovar et al 2007;Likić et al in press). …”

Mitosomes of Entamoeba histolytica are abundant mitochondrion-related remnant organelles that lack a detectable organellar genome

“…Some, such as those of Entamoeba and Cryptosporidium, have been shown to contain chaperonin Cpn60, a protein known to participate in the refolding of imported proteins (Sigler et al, 1998; Mai et al, 1999;Tovar et al, 1999;Riordan et al, 2003); mitosomes of Trachipleistophora contain a mitochondrialtype Hsp70 (mtHsp70), a molecular motor that helps internalize proteins into the organelle (Matouschek et al, 2000;Williams et al, 2002). Other proteins have also been suggested as putative mitosomal components in various amitochondrial lineages but their cellular localization has not been demonstrated experimentally (Clark & Roger, 1995;Bakatselou et al, 2000Bakatselou et al, , 2003Katinka et al, 2001;Morrison et al, 2001;Zhu & Keithly, 2002;Arisue et al, 2002). Perhaps the most significant finding in relation to the biology of mitosomes is the direct demonstration that Giardia mitosomes function in the biosynthesis of molecular iron-sulphur (Fe-S) clusters and in their subsequent incorporation into functional Fe-S proteins (Tovar et al, 2003).…”

DNA characterization of simian Entamoeba histolytica-like strains to differentiate them from Entamoeba histolytica

“…b Simian E. histolytica-like strainspecific block insertions. c EHMfas1-specific block insertion and 5.8S rDNA with ITS 1 and ITS 2 and Cpn60 and PNT genes of EHMfas1 and P19-061405 have been used for previous phylogenetic studies of the genus Entamoeba (Clark and Diamond 1997;Silberman et al 1999;Som et al 2000;Bakatselou et al 2003;Clark et al 2006). All phylogenetic studies indicated that EHMfas1 and P19-061405 generated an original cluster beside or under E. histolytica, including the PNT gene, which is known to contribute to an anomalous-shaped phylogenetic tree (Bakatselou et al 2003).…”