Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:1.12.7.2 (hydrogenase)
 3,522 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nickel is a component of the H2-oxidizing hydrogenase of many bacteria. We report that nickel is required not only for the activity of the Bradyrhizobium japonicum H2 uptake (hup) enzyme but also for the initiation of its transcription. A much greater level of hydrogenase-specific mRNA was detected in cells that were derepressed for hydrogenase in the presence of 5 microM nickel than in the absence of nickel. Control experiments involving probing of mRNA with a B. japonicum gene encoding a non-nickel-containing protein (delta-aminolevulinic acid synthetase) demonstrated that there was no influence by nickel levels on its message. Assays utilizing a plasmid-borne gene fusion linking the 5' upstream sequence of the hup locus to a promoterless beta-Gal structural gene demonstrated that an upstream region between -239 and -168 is critical for transcriptional regulation by nickel. Hydrogenase transcription is not self-regulated by the nickel-containing hydrogenase as the hydrogenase promoter was still regulated by nickel in a mutant strain containing a Tn5 insertion in the hup structural gene. This is the first report of transcriptional regulation of a protein by nickel.
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PMID:Transcriptional regulation of hydrogenase synthesis by nickel in Bradyrhizobium japonicum. 212 29

Plasmid-borne hup-lacZ transcriptional fusion constructs were introduced into three separate mutant strains of Bradyrhizobium japonicum which express hydrogenase constitutively (Hupc strains SR470, SR473 and JH101) in both autotrophic and heterotrophic environments. The lacZ structural gene linked directly to the regulatory region upstream of the hydrogenase structural gene encompassing -149 bases expressed beta-gal at a constant, high level, in response to various concentrations of Ni (0 microM to 1 microM). beta-Gal activity was expressed at a constant level in response to variations in concentration of O2 (0%-10%) and H2 (0%-10%) as well. The cis-acting region required to express hydrogenase constitutively is located between -149 and -98 bases. This is also the site of nickel, oxygen and hydrogen-dependent regulatory action in the wild-type strain. It is postulated that a single mutation in Hupc strains affects the trans-acting factor which would normally by responsive to Ni, O2 and H2.
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PMID:Expression of hydrogenase in Hupc strains of Bradyrhizobium japonicum. 835 50