HoxA is a transcriptional regulator for expression of the <i>hup</i> structural genes in free‐living <i>Bradyrhizobium japonicum</i>

Soom, Carolien Van; Wilde, P. de; Vanderleyden, Jos

doi:10.1046/j.1365-2958.1997.2781648.x

Cited by 29 publications

(23 citation statements)

References 50 publications

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“…A similar arrangement of genes is seen in Bradyrhizobium japonicum (4,41). R. palustris has homologues of a set of uptake hydrogenase regulatory genes that has been characterized in Rhodobacter capsulatus (10,11,13), Ralstonia eutropha (3,24,26,27), and B. japonicum (1,40). It has hupU (RPA0959) and hupV (RPA0960) genes predicted to encode a hydrogen sensor protein.…”

Section: Resultsmentioning

confidence: 90%

Regulation of Uptake Hydrogenase and Effects of Hydrogen Utilization on Gene Expression in Rhodopseudomonas palustris

2006

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Rhodopseudomonas palustris is a purple, facultatively phototrophic bacterium that uses hydrogen gas as an electron donor for carbon dioxide fixation during photoautotrophic growth or for ammonia synthesis during nitrogen fixation. It also uses hydrogen as an electron supplement to enable the complete assimilation of oxidized carbon compounds, such as malate, into cell material during photoheterotrophic growth. The R. palustris genome predicts a membrane-bound nickel-iron uptake hydrogenase and several regulatory proteins to control hydrogenase synthesis. There is also a novel sensor kinase gene (RPA0981) directly adjacent to the hydrogenase gene cluster. Here we show that the R. palustris regulatory sensor hydrogenase HupUV acts in conjunction with the sensor kinase-response regulator protein pair HoxJHoxA to activate hydrogenase expression in response to hydrogen gas. Transcriptome analysis indicated that the HupUV-HoxJA regulatory system also controls the expression of genes encoding a predicted dicarboxylic acid transport system, a putative formate transporter, and a glutamine synthetase. RPA0981 had a small effect in repressing hydrogenase synthesis. We also determined that the two-component system RegS-RegR repressed expression of the uptake hydrogenase, probably in response to changes in intracellular redox status. Transcriptome analysis indicated that about 30 genes were differentially expressed in R. palustris cells that utilized hydrogen when growing photoheterotrophically on malate under nitrogenfixing conditions compared to a mutant strain that lacked uptake hydrogenase. From this it appears that the recycling of reductant in the form of hydrogen does not have extensive nonspecific effects on gene expression in R. palustris.Nitrogenases convert nitrogen gas to ammonia, with the concomitant obligate production of hydrogen, a biofuel (16, 38). The purple, facultatively photosynthetic bacterium Rhodopseudomonas palustris has promise for eventual use in a biological process for hydrogen production because it has three nitrogenase isozymes, can generate the ATP needed for hydrogen production by photophosphorylation, and can access acetate and lignin monomers as sources of electrons for hydrogen synthesis (25,29). A potential complication of using R. palustris for hydrogen production is that it has a propensity to take up and utilize any available external hydrogen for a variety of different metabolic functions. It takes up hydrogen to supply reductant needed for ammonia production by the process of nitrogen fixation. It uses hydrogen gas as an electron donor for photoautotrophic growth with sodium bicarbonate. In addition, by analogy with work with other purple nonsulfur phototrophs, we would expect R. palustris to use hydrogen gas as an electron supplement to allow the reduction of oxidized organic compounds during photoheterotrophic growth (21). In this way, cells can completely assimilate into biomass compounds such as malate that are relatively more oxidized than cell material.Hydrogen utilization is t...

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Section: Resultsmentioning

confidence: 90%

Regulation of Uptake Hydrogenase and Effects of Hydrogen Utilization on Gene Expression in Rhodopseudomonas palustris

2006

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“…The transduction pathway that responds specifically to H 2 has been studied in Bradyrhizobium japonicum (41)(42)(43) and, in more detail, in R. eutropha (3,23,26,27) and R. capsulatus (13,16,18,40). This pathway comprises the three proteins HupUV, HupT, and HupR in R. capsulatus.…”

Section: Discussionmentioning

confidence: 99%

Interaction between the H ₂ Sensor HupUV and the Histidine Kinase HupT Controls HupSL HydrogenaseSynthesis in Rhodobactercapsulatus

2003

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The photosynthetic bacterium Rhodobacter capsulatus contains two [NiFe]hydrogenases: an energy-generating hydrogenase, HupSL, and a regulatory hydrogenase, HupUV. The synthesis of HupSL is specifically activated by H 2 through a signal transduction cascade comprising three proteins: the H 2 -sensing HupUV protein, the histidine kinase HupT, and the transcriptional regulator HupR. Whereas a phosphotransfer between HupT and HupR was previously demonstrated, interaction between HupUV and HupT was only hypothesized based on in vivo analyses of mutant phenotypes. To visualize the in vitro interaction between HupUV and HupT proteins, a six-His (His 6 )-HupU fusion protein and the HupV protein were coproduced by using a homologous expression system. The two proteins copurified as a His 6 -HupUHupV complex present in dimeric and tetrameric forms, both of which had H 2 uptake activity. We demonstrated that HupT and HupUV interact and form stable complexes that could be separated on a native gel. Interaction was also monitored with surface plasmon resonance technology and was shown to be insensitive to salt concentration and pH changes, suggesting that the interactions involve hydrophobic residues. As expected, H 2 affects the interaction between HupUV and HupT, leading to a weakening of the interaction, which is independent of the phosphate status of HupT. Several forms of HupT were tested for their ability to interact with HupUV and to complement hupT mutants. Strong interaction with HupUV was obtained with the isolated PAS domain of HupT and with inactive HupT mutated in the phosphorylable histidine residue, but only the wild-type HupT protein was able to restore normal H 2 regulation.

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“…The controlling promoters of genes encoding chimeric hydrogenases of hydrogenoxidizing bacteria have also been characterized (8,35,50). In most of the cases, sequence elements resembling a Ϫ24/Ϫ12 consensus sequence of 54 -dependent promoters are located just upstream of the transcription start (39).…”

Section: Discussionmentioning

confidence: 99%

Transcriptional and Mutational Analysis of the Uptake Hydrogenase of the Filamentous Cyanobacterium Anabaena variabilis ATCC 29413

2000

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A 10-kb DNA region of the cyanobacterium Anabaena variabilis ATCC 29413 containing the structural genes of the uptake hydrogenase (hupSL) was cloned and sequenced. In contrast to the hupL gene of Anabaena sp. strain PCC 7120, which is interrupted by a 10.5-kb DNA fragment in vegetative cells, there is no programmed rearrangement within the hupL gene during the heterocyst differentiation of A. variabilis. The hupSL genes were transcribed as a 2.7-kb operon and were induced only under nitrogen-fixing conditions, as shown by Northern blot experiments and reverse transcriptase PCR. Primer extension experiments with a fluorescence-labeled oligonucleotide primer confirmed these results and identified the 5 start of the mRNA transcript 103 bp upstream of the ATG initiation codon. A consensus sequence in the promoter that is recognized by the fumarate nitrate reductase regulator (Fnr) could be detected. The hupSL operon in A. variabilis was interrupted by an interposon deletion (mutant strain AVM13). Under N 2 -fixing conditions, the mutant strain exhibited significantly increased rates in H 2 accumulation and produced three times more hydrogen than the wild type. These results indicate that the uptake hydrogenase is catalytically active in the wild type and that the enzyme reoxidizes the H 2 developed by the nitrogenase. The Nif phenotype of the mutant strain showed a slight decrease of acetylene reduction compared to that of the wild type.The only microorganisms with an O 2 -producing photosynthesis that have a hydrogen metabolism are cyanobacteria and green algae (23,25). In cyanobacteria, up to three enzymes can be involved in hydrogen metabolism: the nitrogenase which produces H 2 during nitrogen fixation (24), the membranebound hydrogenase which reoxidizes the H 2 (10), and the bidirectional hydrogenase catalyzing both oxidation of molecular hydrogen and reduction of protons (38). In cyanobacteria, the genetics of bidirectional hydrogenases are especially well characterized (3, 7). But, the H 2 production in filamentous cyanobacteria during the reduction of nitrogen to NH 3 is mainly catalyzed by the nitrogenase in the heterocysts. The Anabaena cells can oxidize the hydrogen with the uptake hydrogenase via the oxyhydrogen (Knallgas) reaction. It was suggested that the organism gets additional ATP while the Knallgas reaction can protect the O 2 -sensitive nitrogenase by removing the oxygen in the heterocysts (30).Hydrogenases have been described for a large number of microorganisms and studied intensively in diverse phylogenetic groups of bacteria (22,34,54). The uptake hydrogenases are membrane-bound enzymes which consist of two subunits with [Fe-S] clusters as prosthetic groups. The large subunit, HupL, carries additionally a Ni atom in the active center. In most of the bacterial families, the hupSL genes are clustered in an operon in which hupS is located upstream of the hupL gene (20,51,53). Recently, some hydrogenase sequences from filamentous cyanobacteria were published (10, 31, 38). The uptake hydrogenase i...

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HoxA is a transcriptional regulator for expression of the hup structural genes in free‐living Bradyrhizobium japonicum

Cited by 29 publications

References 50 publications

Regulation of Uptake Hydrogenase and Effects of Hydrogen Utilization on Gene Expression in Rhodopseudomonas palustris

Regulation of Uptake Hydrogenase and Effects of Hydrogen Utilization on Gene Expression in Rhodopseudomonas palustris

Interaction between the H ₂ Sensor HupUV and the Histidine Kinase HupT Controls HupSL HydrogenaseSynthesis in Rhodobactercapsulatus

Transcriptional and Mutational Analysis of the Uptake Hydrogenase of the Filamentous Cyanobacterium Anabaena variabilis ATCC 29413

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HoxA is a transcriptional regulator for expression of the hup structural genes in free‐living Bradyrhizobium japonicum

Cited by 29 publications

References 50 publications

Regulation of Uptake Hydrogenase and Effects of Hydrogen Utilization on Gene Expression in Rhodopseudomonas palustris

Regulation of Uptake Hydrogenase and Effects of Hydrogen Utilization on Gene Expression in Rhodopseudomonas palustris

Interaction between the H 2 Sensor HupUV and the Histidine Kinase HupT Controls HupSL HydrogenaseSynthesis in Rhodobactercapsulatus

Transcriptional and Mutational Analysis of the Uptake Hydrogenase of the Filamentous Cyanobacterium Anabaena variabilis ATCC 29413

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Interaction between the H ₂ Sensor HupUV and the Histidine Kinase HupT Controls HupSL HydrogenaseSynthesis in Rhodobactercapsulatus