Abstract
The RpoS and PsrA proteins are key transcriptional regulators that are activated in response to the stationary phase of growth in pseudomonads. This study was designed to establish whether ClpXP (ATP-dependent serine protease) regulates levels of RpoS and PsrA in Pseudomonas putida WCS358. Western blot analysis of P. putida WCS358 protein extracts from the early exponentianl, late exponential, and stationary phases of growth with antibodies against RpoS and PsrA revealed that these proteins are degraded by ClpXP in the early exponential phase of growth. The obtained results demonstrate a role for ClpXP protease in post-translational regulation of proteins encoded by the rpoS and psrA genes in Pseudomonas spp.
Highlights
Gram-negative bacteria have evolved sophisticated stress response mechanisms that allow them to adapt to a broad range of stressful conditions
Bacteria were grown in LB medium (1% tripton, 0.5% NaCl, and 0.5% yeast extract) with addition of kanamycin (100 μg/ml) for P. putida WCS358 clpX::Km, P. putida WCS358 rpoS::Km and P. putida WCS358 psrA::Km
In order to determine the role of ClpXP protease in post-translational regulation of the rpoS and psrA genes of Pseudomonas putida WCS358, cellular protein extracts were isolated from this strain and its clpX, rpoS, and psrA mutants
Summary
Gram-negative bacteria have evolved sophisticated stress response mechanisms that allow them to adapt to a broad range of stressful conditions. The central regulator during the stationary phase in Pseudomonas spp., as in other Gram-negative bacteria, is the stationary phase RpoS alternative sigma factor (Hengge - Aronis , 2002; Jorgensen et al, 1999; S u h et al, 1999). Regulation has been studied to a lesser extent in fluorescent pseudomonads, where – contrary to the case of E. coli - transcriptional regulation plays a major role (Ve nturi , 2003). It has been shown that the TetR family regulator designated PsrA plays a major role in positively regulating rpoS transcription at the entry of pseudomonads into the stationary phase (Kojic and Ve nturi , 2001; Kojic et al, 2002). The role of ClpXP protease in posttranslational regulation of the RpoS and PsrA proteins in Pseudomonas putida WCS358 is described for the first time
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