RESUMO
An extremophile D. radiodurans encodes a non-cold shock inducible cold shock protein homolog DR_0907 (also known as PprM). The DR_0907 ORF was deleted by knockout mutagenesis and the resultant deletion mutant (ΔpprM D. radiodurans) displayed growth defect as well as gamma-radiation sensitivity (D10 valuesâ¯=â¯ΔpprM D. radiodurans: 12.1â¯kGy versus wild type (WT) D. radiodurans: 14â¯kGy). 2D gel based comparative proteomics revealed a comparable induction of DNA repair proteins in ΔpprM D. radiodurans and WT D. radiodurans recovering from 5â¯kGy gamma irradiation (60Co gamma source, dose rate: 2â¯kGy/h), suggesting that pprM does not cause radiation sensitivity through modulation of DdrO-regulated DNA repair genes. However, deletion of pprM did result in repression of several proteins that belonged to vital housekeeping pathways such as metabolism and protein homeostasis that might contribute to slow growth phenotype. These deficiencies intrinsic to ΔpprM D. radiodurans might also contribute to its radiation sensitivity.
Assuntos
Proteínas e Peptídeos de Choque Frio/metabolismo , Deinococcus/genética , Deinococcus/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Reparo do DNA/fisiologia , Raios gama , Pleiotropia Genética/genética , Estresse Oxidativo/genética , Estresse Oxidativo/fisiologia , Proteoma/metabolismo , Tolerância a RadiaçãoRESUMO
The genome of D. radiodurans harbors genes for structural and regulatory proteins of Kdp ATPase, in an operon pattern, on Mega plasmid 1. Organization of its two-component regulatory genes is unique. Here we demonstrate that both, the structural as well as regulatory components of the kdp operon of D. radiodurans are expressed quickly as the cells experience potassium limitation but are not expressed upon increase in osmolarity. The cognate DNA binding response regulator (RR) effects the expression of kdp operon during potassium deficiency through specific interaction with the kdp promoter. Deletion of the gene encoding RR protein renders the mutant D. radiodurans (ΔRR) unable to express kdp operon under potassium limitation. The ΔRR D. radiodurans displays no growth defect when grown on rich media or when exposed to oxidative or heat stress but shows reduced growth following gamma irradiation. The study elucidates the functional and regulatory aspects of the novel kdp operon of this extremophile, for the first time.