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

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.

SUBMITTER: van der Giezen M

PROVIDER: S-EPMC373444 | biostudies-literature | 2004 Feb

REPOSITORIES: biostudies-literature

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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 Mark M Cox Siân S Tovar Jorge J

BMC evolutionary biology 20040220

<h4>Background</h4>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.<h ...[more]

PMID: 15040816

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Project description:All sulfur transfer pathways generally have in common an l-cysteine desulfurase as the initial sulfur-mobilizing enzyme, which serves as a sulfur donor for the biosynthesis of numerous sulfur-containing biomolecules in the cell. In Escherichia coli, the housekeeping l-cysteine desulfurase IscS functions as a hub for sulfur transfer through interactions with several partner proteins, which bind at different sites on IscS. So far, the interaction sites of IscU, Fdx, CyaY, and IscX involved in iron sulfur (Fe-S) cluster assembly, TusA, required for molybdenum cofactor biosynthesis and mnm5s2U34 transfer RNA (tRNA) modifications, and ThiI, involved in both the biosynthesis of thiamine and s4U8 tRNA modifications, have been mapped. Previous studies have suggested that IscS partner proteins bind only one at a time, with the exception of Fe-S cluster assembly, which involves the formation of a ternary complex involving IscS, IscU, and one of CyaY, Fdx, or IscX. Here, we show that the affinity of TusA for IscS is similar to but lower than that of IscU and that these proteins compete for binding to IscS. We show that heterocomplexes involving the IscS dimer and single IscU and TusA molecules are readily formed and that binding of both TusA and IscU to IscS affects its l-cysteine desulfurase activity. A model is proposed in which the delivery of sulfur to different sulfur-requiring pathways is controlled by sulfur acceptor protein levels, IscS-binding affinities, and acceptor protein-modulated IscS desulfurase activity.IMPORTANCEIron-sulfur clusters are evolutionarily ancient prosthetic groups. The housekeeping l-cysteine desulfurase IscS functions as a central core for sulfur transfer through interactions with several partner proteins, which bind at different sites on each IscS monomer with different affinities and partially overlapping binding sites. We show that heterocomplexes involving the IscS dimer and single IscU and TusA molecules at each site of the dimer are formed, thereby influencing the activity of IscS.

Dataset Information

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

Publications

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

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