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Iron-Dependent Hydrogenases of Entamoeba histolytica and Giardia lamblia: Activity of the Recombinant Entamoebic Enzyme and Evidence for Lateral Gene Transfer

Julie E. J. Nixon, Jessica Field, Andrew G. McArthur, Mitchell L. Sogin, Nigel Yarlett, Brendan J. Loftus and John Samuelson
Biological Bulletin
Vol. 204, No. 1 (Feb., 2003), pp. 1-9
DOI: 10.2307/1543490
Stable URL: http://www.jstor.org/stable/1543490
Page Count: 9
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Iron-Dependent Hydrogenases of Entamoeba histolytica and Giardia lamblia: Activity of the Recombinant Entamoebic Enzyme and Evidence for Lateral Gene Transfer
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Abstract

Entamoeba histolytica and Spironucleus barkhanus have genes that encode short iron-dependent hydrogenases (Fe-hydrogenases), even though these protists lack hydrogenosomes. To understand better the biochemistry of the protist Fe-hydrogenases, we prepared a recombinant E. histolytica short Fe-hydrogenase and measured its activity in vitro. A Giardia lamblia gene encoding a short Fe-hydrogenase was identified from shotgun genomic sequences, and RT-PCR showed that cultured entamoebas and giardias transcribe short Fe-hydrogenase mRNAs. A second E. histolytica gene, which encoded a long Fe-hydrogenase, was identified from shotgun genomic sequences. Phylogenetic analyses suggested that the short Fe-hydrogenase genes of entamoeba and diplomonads share a common ancestor, while the long Fe-hydrogenase gene of entamoeba appears to have been laterally transferred from a bacterium. These results are discussed in the context of competing ideas for the origins of genes encoding fermentation enzymes of these protists.

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