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Descripción
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| Nickel is an essential element for different biological processes. Enzymes with nickel atom(s) in their active site participate in urea hydrolysis, oxidation of molecular hydrogen and detoxification of superoxide anion radicals. Nickel transport is a challenge for microorganisms since, although essential, high intracellular levels of this metal are toxic. For this reason, bacteria have developed high affinity nickel transporters as well as nickel-specific detoxification systems. In Rhizobium leguminosarum bv. viciae, a nickel-dependent hydrogenase is induced in pea (Pisum sativum) bacteroids. Symbiotic hydrogen uptake is limited by nickel availability to the bacteroids (Brito et al., 1994), and this nickel-dependent limitation is partly dependent on the plant host (Brito et al., 2008). Proteins involved in nickel transport for hydrogenase synthesis have not been described in R. leguminosarum. One of the putative candidates for this role is HupE, a predicted membrane protein that shows a histidine-rich domain similar to those involved in nickel transporters like HoxN from Ralstonia eutropha or NixA from Helicobacter pylori. In R. leguminosarum bv. viciae UPM791, the gene hupE is part of the hydrogenase gene cluster located in the symbiotic plasmid, whereas a second hupE-like gene, hupE2, lies in the pRLUPM791b plasmid. In addition, this bacterium contains an rcnRA system in the chromosome. In this work, we report the characterization of HupE/HupE2 as a novel class of nickel transporter involved in hydrogen oxidation. In these proteins, histidine residues essential for HupE functionality have been identified. On the other hand, analysis of expression of the rcnRA operon has revealed that these genes are overexpressed in response to high levels of nickel or cobalt in the culture medium. This mode of regulation is consistent with the purported role of these genes as part of a Ni/Co efflux system. | |
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Internacional
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Si |
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Nombre congreso
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8th European Nitrogen Fixation Conference |
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Tipo de participación
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960 |
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Lugar del congreso
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Gante (Bélgica) |
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Revisores
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Si |
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ISBN o ISSN
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CDP08UPM |
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DOI
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Fecha inicio congreso
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30/08/2008 |
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Fecha fin congreso
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03/09/2008 |
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Desde la página
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247 |
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Hasta la página
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247 |
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Título de las actas
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Book of abstracts of 8th European Nitrogen Fixation Conference |