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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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Schematic representation of Isc/Nif operons from different bacteria. Shown is an area of about 10 kb around the IscU/S or NifU/S genes from C. jejuni, H. pylori, A. vinelandii, and E. coli. Isc/Nif genes are indicated by a dark grey box and other genes that are part of the Isc-operon are indicated by a lighter shade of grey. Genes that are not part of the Isc/Nif operon are of yet a lighter shade. Boxes are drawn proportionally with regards to length of the ORF.
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Figure 6: Schematic representation of Isc/Nif operons from different bacteria. Shown is an area of about 10 kb around the IscU/S or NifU/S genes from C. jejuni, H. pylori, A. vinelandii, and E. coli. Isc/Nif genes are indicated by a dark grey box and other genes that are part of the Isc-operon are indicated by a lighter shade of grey. Genes that are not part of the Isc/Nif operon are of yet a lighter shade. Boxes are drawn proportionally with regards to length of the ORF.

Mentions: Analysis of the organization of Isc/Nif loci on the genomes of several bacteria revealed the presence of a small Isc operon consisting exclusively of IscU and IscS in H. pylori and C. jejuni, whilst the well-studied E. coli and A. vinelandii isc operons contained several other genes involved in FeS cluster assembly (see Fig. 6). This observation provides a mechanistic explanation for the presence of two interacting proteins with similar ancestry in the genome of E. histolytica. It is possible that E. histolytica might have incorporated the entire isc operon from Helicobacter/Campylobacter, or from their ancestors, into its genome in a single transfer event. Once freed from the constraints of operon-type prokaryotic gene expression, the iscS/U genes might have become separated in the E. histolytica genome during the course of evolution.


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)

Schematic representation of Isc/Nif operons from different bacteria. Shown is an area of about 10 kb around the IscU/S or NifU/S genes from C. jejuni, H. pylori, A. vinelandii, and E. coli. Isc/Nif genes are indicated by a dark grey box and other genes that are part of the Isc-operon are indicated by a lighter shade of grey. Genes that are not part of the Isc/Nif operon are of yet a lighter shade. Boxes are drawn proportionally with regards to length of the ORF.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC373444&req=5

Figure 6: Schematic representation of Isc/Nif operons from different bacteria. Shown is an area of about 10 kb around the IscU/S or NifU/S genes from C. jejuni, H. pylori, A. vinelandii, and E. coli. Isc/Nif genes are indicated by a dark grey box and other genes that are part of the Isc-operon are indicated by a lighter shade of grey. Genes that are not part of the Isc/Nif operon are of yet a lighter shade. Boxes are drawn proportionally with regards to length of the ORF.
Mentions: Analysis of the organization of Isc/Nif loci on the genomes of several bacteria revealed the presence of a small Isc operon consisting exclusively of IscU and IscS in H. pylori and C. jejuni, whilst the well-studied E. coli and A. vinelandii isc operons contained several other genes involved in FeS cluster assembly (see Fig. 6). This observation provides a mechanistic explanation for the presence of two interacting proteins with similar ancestry in the genome of E. histolytica. It is possible that E. histolytica might have incorporated the entire isc operon from Helicobacter/Campylobacter, or from their ancestors, into its genome in a single transfer event. Once freed from the constraints of operon-type prokaryotic gene expression, the iscS/U genes might have become separated in the E. histolytica genome during the course of evolution.

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