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The iron-sulfur cluster assembly genes iscS and iscU of Entamoeba histolytica were acquired by horizontal gene transfer.

van der Giezen M, Cox S, Tovar J - BMC Evol. Biol. (2004)

Bottom Line: E. histolytica IscU and IscS were found to contain all features considered essential for their biological activity, including amino acid residues involved in substrate and/or co-factor binding.The bacterial-type FeS cluster assembly genes of E. histolytica suggest their lateral acquisition from epsilon proteobacteria.This is a clear example of horizontal gene transfer (HGT) from eubacteria to unicellular eukaryotic organisms, a phenomenon known to contribute significantly to the evolution of eukaryotic genomes.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK. mark.vandergiezen@rhul.ac.uk

ABSTRACT

Background: Iron-sulfur (FeS) proteins are present in all living organisms and play important roles in electron transport and metalloenzyme catalysis. The maturation of FeS proteins in eukaryotes is an essential function of mitochondria, but little is known about this process in amitochondriate eukaryotes. Here we report on the identification and analysis of two genes encoding critical FeS cluster (Isc) biosynthetic proteins from the amitochondriate human pathogen Entamoeba histolytica.

Results: E. histolytica IscU and IscS were found to contain all features considered essential for their biological activity, including amino acid residues involved in substrate and/or co-factor binding. The IscU protein differs significantly from other eukaryotic homologs and resembles the long type isoforms encountered in some bacteria. Phylogenetic analyses of E. histolytica IscS and IscU showed a close relationship with homologs from Helicobacter pylori and Campylobacter jejuni, to the exclusion of mitochondrial isoforms.

Conclusions: The bacterial-type FeS cluster assembly genes of E. histolytica suggest their lateral acquisition from epsilon proteobacteria. This is a clear example of horizontal gene transfer (HGT) from eubacteria to unicellular eukaryotic organisms, a phenomenon known to contribute significantly to the evolution of eukaryotic genomes.

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Phylogenetic analysis of E. histolytica IscS and IscU protein sequences using a similar taxonomic sampling. Depicted are unrooted maximum likelihood phylogenetic trees of 29 IscS (left) and 28 IscU (right) protein sequences. The E. histolytica sequences are recovered as part of a well supported monophyletic group comprising the gut bacteria H. pylori and C. jejuni. The orange branches represent those sequences containing the long IscU isoform. Numbers in red represent posterior probabilities as determined by MrBayes [55] where a value of 1.0 represents maximum support (only values above 0.75 are shown). Values in blue represent bootstrap values as determined using PHYML [57], only bootstrap values above 50% are shown.
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Figure 5: Phylogenetic analysis of E. histolytica IscS and IscU protein sequences using a similar taxonomic sampling. Depicted are unrooted maximum likelihood phylogenetic trees of 29 IscS (left) and 28 IscU (right) protein sequences. The E. histolytica sequences are recovered as part of a well supported monophyletic group comprising the gut bacteria H. pylori and C. jejuni. The orange branches represent those sequences containing the long IscU isoform. Numbers in red represent posterior probabilities as determined by MrBayes [55] where a value of 1.0 represents maximum support (only values above 0.75 are shown). Values in blue represent bootstrap values as determined using PHYML [57], only bootstrap values above 50% are shown.

Mentions: Bayesian and maximum likelihood (ML) phylogenetic analyses of E. histolytica IscU and IscS protein sequences revealed that the Entamoeba Isc proteins form a well supported clade with Helicobacter pylori and Campylobacter jejuni – two bacteria encountered in the human digestive tract – to the exclusion of all other prokaryotic and eukaryotic homologs (Fig. 5). All three independent Bayesian analyses converged on the same tree with similar posterior probabilities. For IscU, the ML tree had a slightly better likelihood than the Bayesian tree, while for IscS both trees had similar likelihoods. The overall topologies of IscS and IscU phylogenetic trees are very similar to each other and major taxonomic clades like plants, animals, and fungi are well conserved. The position of the microsporidium Encephalitozoon cuniculi in the IscU tree is poorly resolved as indicated by the very low support for this node at the base of the metazoa, contrary to its well-documented association with fungi [36].


The iron-sulfur cluster assembly genes iscS and iscU of Entamoeba histolytica were acquired by horizontal gene transfer.

van der Giezen M, Cox S, Tovar J - BMC Evol. Biol. (2004)

Phylogenetic analysis of E. histolytica IscS and IscU protein sequences using a similar taxonomic sampling. Depicted are unrooted maximum likelihood phylogenetic trees of 29 IscS (left) and 28 IscU (right) protein sequences. The E. histolytica sequences are recovered as part of a well supported monophyletic group comprising the gut bacteria H. pylori and C. jejuni. The orange branches represent those sequences containing the long IscU isoform. Numbers in red represent posterior probabilities as determined by MrBayes [55] where a value of 1.0 represents maximum support (only values above 0.75 are shown). Values in blue represent bootstrap values as determined using PHYML [57], only bootstrap values above 50% are shown.
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Related In: Results  -  Collection

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Figure 5: Phylogenetic analysis of E. histolytica IscS and IscU protein sequences using a similar taxonomic sampling. Depicted are unrooted maximum likelihood phylogenetic trees of 29 IscS (left) and 28 IscU (right) protein sequences. The E. histolytica sequences are recovered as part of a well supported monophyletic group comprising the gut bacteria H. pylori and C. jejuni. The orange branches represent those sequences containing the long IscU isoform. Numbers in red represent posterior probabilities as determined by MrBayes [55] where a value of 1.0 represents maximum support (only values above 0.75 are shown). Values in blue represent bootstrap values as determined using PHYML [57], only bootstrap values above 50% are shown.
Mentions: Bayesian and maximum likelihood (ML) phylogenetic analyses of E. histolytica IscU and IscS protein sequences revealed that the Entamoeba Isc proteins form a well supported clade with Helicobacter pylori and Campylobacter jejuni – two bacteria encountered in the human digestive tract – to the exclusion of all other prokaryotic and eukaryotic homologs (Fig. 5). All three independent Bayesian analyses converged on the same tree with similar posterior probabilities. For IscU, the ML tree had a slightly better likelihood than the Bayesian tree, while for IscS both trees had similar likelihoods. The overall topologies of IscS and IscU phylogenetic trees are very similar to each other and major taxonomic clades like plants, animals, and fungi are well conserved. The position of the microsporidium Encephalitozoon cuniculi in the IscU tree is poorly resolved as indicated by the very low support for this node at the base of the metazoa, contrary to its well-documented association with fungi [36].

Bottom Line: E. histolytica IscU and IscS were found to contain all features considered essential for their biological activity, including amino acid residues involved in substrate and/or co-factor binding.The bacterial-type FeS cluster assembly genes of E. histolytica suggest their lateral acquisition from epsilon proteobacteria.This is a clear example of horizontal gene transfer (HGT) from eubacteria to unicellular eukaryotic organisms, a phenomenon known to contribute significantly to the evolution of eukaryotic genomes.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Biological Sciences, Royal Holloway, University of London, Egham, Surrey TW20 0EX, UK. mark.vandergiezen@rhul.ac.uk

ABSTRACT

Background: Iron-sulfur (FeS) proteins are present in all living organisms and play important roles in electron transport and metalloenzyme catalysis. The maturation of FeS proteins in eukaryotes is an essential function of mitochondria, but little is known about this process in amitochondriate eukaryotes. Here we report on the identification and analysis of two genes encoding critical FeS cluster (Isc) biosynthetic proteins from the amitochondriate human pathogen Entamoeba histolytica.

Results: E. histolytica IscU and IscS were found to contain all features considered essential for their biological activity, including amino acid residues involved in substrate and/or co-factor binding. The IscU protein differs significantly from other eukaryotic homologs and resembles the long type isoforms encountered in some bacteria. Phylogenetic analyses of E. histolytica IscS and IscU showed a close relationship with homologs from Helicobacter pylori and Campylobacter jejuni, to the exclusion of mitochondrial isoforms.

Conclusions: The bacterial-type FeS cluster assembly genes of E. histolytica suggest their lateral acquisition from epsilon proteobacteria. This is a clear example of horizontal gene transfer (HGT) from eubacteria to unicellular eukaryotic organisms, a phenomenon known to contribute significantly to the evolution of eukaryotic genomes.

Show MeSH