Disease relevance of nifH1

• The genes encoding the structural components of nitrogenase, nifH, nifD and nifK, from the fast-growing, broad-host-range Rhizobium strain ANU240 have been identified and characterized [1].
• Placement of the UAS from the Bradyrhizobium japonicum nifH gene in front of the spacer (DNA region between URS and promoter) plus promoter from fdhF renders fdhF expression activatable by the Klebsiella pneumoniae NIFA protein, both under aerobic and anaerobic conditions [2].
• Activation of the Bradyrhizobium japonicum nifH and nifDK operons is dependent on promoter-upstream DNA sequences [3].
• Previous analysis of B. japonicum nifH'- and nifD'-'lacZ translational fusions showed that these promoters could be activated by the K. pneumoniae nifA plus the E. coli ntrA gene products [3].
• In a comparison of nifH DNA sequences from T. ferrooxidans and eight other nitrogen-fixing microbes, a Rhizobium sp. isolated from Parasponia andersonii showed the greatest homology (74%) and Clostridium pasteurianum (nifH 1) showed the least homology (54%) [4].

High impact information on nifH1

• NIFA-mediated activation of transcription from the nifH promoter of Klebsiella pneumoniae is greatly stimulated by the integration host factor IHF, which binds to a site between the upstream binding site for NIFA and the promoter, and bends the DNA [5].
• The R. meliloti nifH promoter but not the K. pneumoniae nifH promoter showed sigma 54-dependent methylation protection of guanine residues at -14, -25 and -26, the most conserved nucleotides characteristic of sigma 54-dependent promoters [6].
• The nodD and nifH genes were located on these plasmids, and their sequences were obtained [7].
• To track the extent and architecture of gene conversions, evenly spaced nucleotide changes were made in one of the nitrogenase structural genes (nifH), introducing unique sites for different restriction endonucleases [8].
• Engineering the nifH promoter region and abolishing poly-beta-hydroxybutyrate accumulation in Rhizobium etli enhance nitrogen fixation in symbiosis with Phaseolus vulgaris [9].

Biological context of nifH1

• In a comparison of the amino acid sequences of the Fe proteins, the Rhizobium sp. and Rhizobium japonicum showed the greatest homology (both 86%) and C. pasteurianum (nifH 1 gene product) demonstrated the least homology (56%) to the T. ferrooxidans Fe protein [4].
• Expression of Rhizobium japonicum nifH and nifDK operons can be activated by the Klebsiella pneumonia nifA protein but not by the product of ntrC [10].
• The region upstream of the nifH open reading frame contains a putative promoter whose sequence shows perfect homology with promoters of other diazotrophic bacteria and two putative upstream activator sequences [11].
• A mutant derivative of the K. pneumoniae nifH promoter bearing transitions at positions from -15 to -17 showed sigma 54-dependent methylation protection of guanines -13, -24 and -25 [6].
• Most strains had plasmids, and the presence of plasmid-borne nifH was demonstrated by hybridization for some examples [12].

Associations of nifH1 with chemical compounds

• The amino acid sequence was deduced from the DNA nucleotide sequence of nifH; the polypeptide contains the four cysteine residues highly conserved among other nifH products and an arginine residue at position 101 which could be the site of the modification occurring during the "switch-off" of nitrogenase [11].
• Use of in vivo KMnO4 footprinting to detect single-stranded pyrimidine residues and in vivo methylation protection demonstrated that the sigma 54-dependent protection observed in the R. meliloti and mutant K. pneumoniae nifH promoter results from the formation of a closed promoter complex [6].
• The R. etli rpoN gene was shown to control in free-living conditions the production of melanin, the activation of nifH, and the metabolism of C4-dicarboxylic acids and several nitrogen sources (ammonium, nitrate, alanine, and serine) [13].
• The regulated promoters include the tac promoter which can be induced by IPTG, and nifH promoters which are symbiotically activated in legume nodules [14].
• The phytobeneficial genes nifH (associative nitrogen fixation) and ipdC (synthesis of the phytohormone indoleacetic acid) are chromosomal, but no BAC clone containing both genes was found, pointing to the absence of any genetic island containing nifH and ipdC [15].

Other interactions of nifH1

• Sequence analysis of the nifH gene from each copy, together with partial sequence analysis of the nifD and nifK genes, and restriction endonuclease analysis suggested that the duplication is precise [1].

Analytical, diagnostic and therapeutic context of nifH1

• RFLP analyses of cloned nifH PCR products also revealed characteristic patterns for each sample type [16].
• Studies of high-copy-number nifH promoter constructs showed that partial deletion of the consensus UAS does not alter the ability to inhibit nitrogen fixation by titration of NifA suggesting that NifA can also complex with RNA polymerase containing the alternative sigma-factor RpoN [17].

References