Nucleotide sequence of the rpoN (hno) gene region of Alcaligenes eutrophus: evidence for a conserved gene cluster

Warrelmann, Jürgen; Eitinger, Marita; Schwartz, Edward L.; Römermann, D; Friedrich, Bärbel

doi:10.1007/bf00245213

Cited by 22 publications

(16 citation statements)

References 39 publications

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“…The cloned DNA fragment contains 262 bp of the 5Ј noncoding sequence. Ϫ24/Ϫ12 motifs characteristic of 54 promoters are located upstream of the translational start of the first structural gene, hoxF (Fig. 1).…”

Section: Resultsmentioning

confidence: 99%

“…Sequencing revealed that hoxA encodes a member of the NtrC family of regulatory proteins (12), suggesting a model for hydrogenase regulation that involves transcriptional activation via binding of HoxA upstream of 54 promoters and interaction with 54 RNA polymerase. In order to test the binding of HoxA to hox upstream sequences in vitro, we attempted to purify HoxA.…”

Section: Resultsmentioning

confidence: 99%

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mentioning

confidence: 99%

“…Moreover, hydrogenase synthesis in A. eutrophus is temperature sensitive and abolished above 33ЊC (19). Mutant analysis has shown that the expression of SH-and MBH-encoding genes in A. eutrophus is strictly dependent on two transcriptional components: the minor sigma factor 54 of RNA polymerase (36,54) and the hoxA gene product. Sequence comparisons revealed that the product of hoxA is a member of the family of two-component regulatory systems (12).…”

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Temperature tolerance of hydrogenase expression in Alcaligenes eutrophus is conferred by a single amino acid exchange in the transcriptional activator HoxA

et al. 1995

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Expression of the soluble (SH) and membrane-bound (MBH) hydrogenases in the facultatively lithoautotrophic bacterium Alcaligenes eutrophus is dependent on the transcriptional activator HoxA and the alternative sigma factor 54 . Deletion analysis revealed that a region 170 bp upstream of the transcriptional start of the SH operon is necessary for high-level promoter activity. Mobility shift assays with DNA fragments containing the SH upstream region and purified ␤-galactosidase-HoxA fusion protein isolated from Escherichia coli or authentic HoxA isolated by immunoaffinity chromatography from A. eutrophus failed to detect specific binding. In contrast, A. eutrophus extracts enriched for HoxA by heparin-Sepharose chromatography and ammonium sulfate fractionation produced a weak but discrete shift in the mobility of the target DNA. This effect was not observed with comparable extracts prepared from hoxA mutants. A similar experiment using antibodies against HoxA confirmed that HoxA was responsible for the observed mobility shift. Extracts prepared from a temperature-tolerant mutant of A. eutrophus gave a stronger retardation than did those from the wild type. Unlike the wild type, the hox(Tr) mutant is able to grow with hydrogen at temperatures above 33؇C because of a mutation in the regulatory gene hoxA. In this paper, we show that a single amino acid substitution (Gly-4683Val) in the C-terminal part of HoxA is responsible for temperature tolerance. The SH upstream region also contains sequence motifs resembling the E. coli integration host factor (IHF) binding site, and purified E. coli IHF protein shifted the corresponding indicator fragment.Alcaligenes eutrophus, a member of the ␤ subgroup of the class Proteobacteria, can grow lithoautotrophically with hydrogen as the sole energy source and carbon dioxide as the carbon source (reviewed in reference 3). The bacterium harbors a large plasmid on which the genes required for hydrogen oxidation are located. The hox region encodes two hydrogenases: a cytoplasmic NAD-reducing enzyme (SH) and a membranebound electron transport-coupled protein (MBH). Both hydrogenases belong to the family of nickel-iron-containing proteins. The formation of these metalloproteins is an extremely complex and apparently highly conserved process requiring sets of ancillary functions in addition to the hydrogenase enzymes (reviewed in reference 17). The genes coding for these proteins are part of the hox gene complex in A. eutrophus. Their products are involved in nickel uptake (14), metal processing (9), and hydrogenase maturation (24).Physiological experiments have demonstrated that the synthesis of the two hydrogenases of A. eutrophus is coordinately regulated. Tight repression is observed during growth of the cells on preferentially utilized carbon sources, whereas derepression occurs on poor substrates even in the absence of hydrogen (18). Moreover, hydrogenase synthesis in A. eutrophus is temperature sensitive and abolished above 33ЊC (19). Mutant analysis has shown that the expression ...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…

…”

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confidence: 99%

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Temperature tolerance of hydrogenase expression in Alcaligenes eutrophus is conferred by a single amino acid exchange in the transcriptional activator HoxA

et al. 1995

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“…One additional ORF was however present in R. metallidurans CH34 (orf95), at the same relative location as orf99, present near rpoN in R. eutropha H16 (Warrelmann et al, 1992). Despite their nucleotide sequence similarity, CH34 orf95 and H16 orf99 translated into products which displayed no similarity with each other or any protein in the databases.…”

Section: Discussionmentioning

confidence: 99%