Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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 sigma 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 beta-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 degrees C because of a mutation in the regulatory gene hoxA. In this paper, we show that a single amino acid substitution (Gly-468-->Val) 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.
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PMID:Temperature tolerance of hydrogenase expression in Alcaligenes eutrophus is conferred by a single amino acid exchange in the transcriptional activator HoxA. 773 Feb 67

Heterologous complementation studies using Alcaligenes eutrophus H16 as a recipient identified a hydrogenase-specific regulatory DNA region on megaplasmid pHG21-a of the related species Alcaligenes hydrogenophilus. Nucleotide sequence analysis revealed four open reading frames on the subcloned DNA, designated hoxA, hoxB, hoxC, and hoxJ. The product of hoxA is homologous to a transcriptional activator of the family of two-component regulatory systems present in a number of H2-oxidizing bacteria. hoxB and hoxC predict polypeptides of 34.5 and 52.5 kDa, respectively, which resemble the small and the large subunits of [NiFe] hydrogenases and correlate with putative regulatory proteins of Bradyrhizobium japonicum (HupU and HupV) and Rhodobacter capsulatus (HupU). hoxJ encodes a protein with typical consensus motifs of histidine protein kinases. Introduction of the complete set of genes on a broad-host-range plasmid into A. eutrophus H16 caused severe repression of soluble and membrane-bound hydrogenase (SH and MBH, respectively) synthesis in the absence of H2. This repression was released by truncation of hoxJ. H2-dependent hydrogenase gene transcription is a typical feature of A. hydrogenophilus and differs from the energy and carbon source-responding, H2-independent mode of control characteristic of A. eutrophus H16. Disruption of the A. hydrogenophilus hoxJ gene by an in-frame deletion on megaplasmid pHG21-a led to conversion of the regulatory phenotype: SH and MBH of the mutant were expressed in the absence of H2 in response to the availability of the carbon and energy source. RNA dot blot analysis showed that HoxJ functions on the transcriptional level. These results suggest that the putative histidine protein kinase HoxJ is involved in sensing molecular hydrogen, possibly in conjunction with the hydrogenase-like polypeptides HoxB and HoxC.
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PMID:A hydrogen-sensing system in transcriptional regulation of hydrogenase gene expression in Alcaligenes species. 904 26