Description

More than 7% of the Pseudomonas aeruginosa genes are encoding transcriptional regulators, many of which with unknown functions. Among them, those belonging to the LysR family are the most represented. The PA4203 gene lies upstream of the previously characterized ppgL gene (PA4204), which encodes a periplasmic gluconolactonase, which detoxifies gluconolactone by converting it to gluconate. Upstream of PA4203 and in the opposite orientation are the PA4202 gene coding for a nitronate monooxygenase and ddlA (PA4201) encoding a D-alanine alanine ligase. This genetic organization is conserved in all P. aeruginosa genomes, but not in other pseudomonads. The intergenic regions between PA4203 and ppgL, and PA4202 are very short (79 and 107 nucleotides, respectively). PA4203 is a repressor of PA4202 and of its own transcription. A chromatin immunoprecipation analysis confirmed the presence of a single PA4203 binding site between PA4202 and PA4203. Electrophoretic mobility shift assays (EMSAs) with the purified PA4203 protein and in41 gel footprinting with the 1, 10-phenanthroline-copper ion, combined with primer extension analysis to determine transcriptional startpoints allowed the identification of a LysR binding motive in the PA4202 and PA4203 intergenic region. Despite this, a transcriptome analysis revealed more genes to be affected in a PA4203 mutant, likely due to the overexpression of the nitronate monooxygenase (PA4202). Deletion of the PA4202 gene resulted in an increased sensitivity of the cells to 3- nitropropionic acid (3-NPA).

Publication Title

Pseudomonas aeruginosa LysR PA4203 regulator NmoR acts as a repressor of the PA4202 nmoA gene, encoding a nitronate monooxygenase.

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