Disease relevance of fixJ

• A gene bank of Azorhizobium caulinodans DNA constructed in the bacteriophage lambda GEM11 was screened with Rhizobium meliloti fixL and fixJ genes as probes [1].
• Rhizobium meliloti regulatory gene fixJ activates transcription of R. meliloti nifA and fixK genes in Escherichia coli [2].
• The sensor kinase FixL and the response regulator FixJ induce the expression of the nitrogen fixation genes of Rhizobium meliloti in response to microaerobiosis, which is a characteristic feature of the plant root nodule interior where the bacteria fix nitrogen [3].

High impact information on fixJ

• The fixL product seems to be a transmembrane sensor that modulates the activity of the fixJ product, a cytoplasmic regulator [4].
• Kanamycin cartridges were inserted into the cloned fixL and fixJ genes and recombined into the host genome [1].
• Bacterial mutants (fixJ and nifD) and a subset of plant mutants (dnf2, dnf3, dnf4, dnf6, and dnf7) defective for nitrogen fixation induce the above genes [5].
• In order to identify the FixLJ regulon, gene expression profiles were determined in microaerobic free-living cells as well as during the symbiotic life of the bacterium for the wild type and a fixJ null-mutant strain [6].
• Attempts at separating the upstream and downstream regions of the nifA promoter so as to maintain fixJ-dependent activity were unsuccessful [7].

Biological context of fixJ

• Two open reading frames of 1512bp and 613bp were identified as fixL and fixJ [1].
• Thus FixJ binding sites appear to be preferentially associated with the pSymA replicon, which carries the fixJ gene [8].
• The genes responsible for sensing and transducing the low oxygen signal, fixL and fixJ, encode proteins (FixL and FixJ, respectively) that are homologous to a large family of bacterial proteins involved in signal transduction, the two component regulatory system proteins [9].

Associations of fixJ with chemical compounds

• In microaerobic conditions the membrane-bound kinase FixL uses ATP to transphosphorylate a histidine residue, and the response regulator FixJ transfers the phosphoryl group from the phosphohistidine to one of its own aspartate residues in a Mg(2+)-dependent mechanism [10].

Regulatory relationships of fixJ

• A sequence comparison of the -54 to -39 region of nifAp with the upstream sequences of fixKp does not reveal a block of identical nucleotides that could account for the fixJ-dependent microaerobic induction of both promoters [7].

Other interactions of fixJ

• The remaining seven loci showed fixL- and fixJ-independent induction of expression in response to oxygen limitation [11].

References