D-GIu, an essential component of peptidoglycans, can be utilized as a carbon and nitrogen source by Pseudomonas aeruginosa. DNA microarrays were employed to identify genes involved in d-Glu catabolism. Through gene knockout and growth phenotype analysis, the divergent dguR-dguABC (d-GIu utilization) gene cluster was shown to participate in D-GIu and D-GIn catabolism and regulation. Growth of the dguR and dguA mutants was abolished completely on d-GIu or retarded on D-GIn as the sole source of carbon and/or nitrogen. The dguA gene encoded a FAD-dependent D-amino acid dehydrogenase with d-GIu as its preferred substrate, and its promoter was specifically induced by exogenous d-GIu and D-GIn. The function of DguR as a transcriptional activator of the dguABC operon was demonstrated by promoter activity measurements in vivo and by mobility shift assays with purified His-tagged DguR in vitro. Although the DNA-binding activity of DguR did not require D-GIu, the presence of D-GIu, but not D-GIn, in the binding reaction was found to stabilize a preferred nucleoprotein complex. The presence of a putative DguR operator was revealed by in silica analysis of the dguR-dguA intergenic regions among Pseudomonas spp. and binding of DguR to a highly conserved 19 bp sequence motif was further demonstrated. The dguB gene encodes a putative enamine/imine deaminase of the RidA family, but its role in d-GIu catabolism remains to be determined. Whilst a lesion in dguC encoding a periplasmic solute binding protein only affected growth on d-GIu slightly, expression of the previously characterized AatJMQP transporter for acidic L-amino acid uptake was found inducible by d-GIu and essential for d-GIu utilization. In summary, the findings of this study supported DguA as a new member of the FAD-dependent D-amino acid dehydrogenase family, and DguR as a D-Glu sensor and transcriptional activator of the dguA promoter.
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