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The ClpP Peptidase Is the Major Determinant of Bulk Protein Turnover in Bacillus subtilis. Holger Kock, 2004.Measurements of overall protein degradation rates in wild-type and clpP mutant Bacillus subtilis cells revealed that stress- or starvation-induced bulk protein turnover depends virtually exclusively on the ClpP peptidase . ClpP is also essential for intracellular protein quality control, and in its absence newly synthesized proteins were highly prone to aggregation even at 37°C . Proteomic comparisons between the wild type and a  clpP
mutant showed that the absence of ClpP leads to severe perturbations
of "normal" physiology, complicating the detection of ClpP
substrates . A pulse-chase two-dimensional gel approach was therefore
used to compare wild-type and clpP mutant cultures that had
been radiolabeled in mid-exponential phase, by quantifying changes in
relative spot intensities with time . The results showed that overall
proteolysis is biased toward proteins with vegetative functions which
are no longer required (or are required at lower levels) in the
nongrowing state . The identified substrate candidates for
ClpP-dependent degradation include metabolic enzymes and
aminoacyl-tRNA synthetases . Some substrate candidates catalyze the
first committed step of certain biosynthetic pathways . Our data
suggest that ClpP-dependent proteolysis spans a broad physiological
spectrum, with regulatory processing of key metabolic components and
regulatory proteins on the one side and general bulk protein
breakdown at the transition from growing to nongrowing phases on the
other .
Plant Lectin-Like Bacteriocin from a Rhizosphere-Colonizing Pseudomonas Isolate. Annabel H. A. Parret, 2003.Rhizosphere isolate Pseudomonas sp . strain BW11M1, which belongs to the Pseudomonas putida cluster, secretes a heat- and protease-sensitive bacteriocin which kills P . putida GR12-2R3 . The production of this bacteriocin is enhanced by DNA-damaging treatment of producer cells . We isolated a TnMod mutant of strain BW11M1 that had lost the capacity to inhibit the growth of strain GR12-2R3 . A wild-type genomic fragment encompassing the transposon insertion site was shown to confer the bacteriocin phenotype when it was introduced into Escherichia coli cells . The bacteriocin structural gene was identified by defining the minimal region required for expression in E . coli . This gene was designated llpA (lectin-like putidacin) on the basis of significant homology of its 276-amino-acid product with mannose-binding lectins from monocotyledonous plants . LlpA is composed of two monocot mannose-binding lectin (MMBL) domains . Several uncharacterized bacterial genes encoding diverse proteins containing one or two MMBL domains were identified . A phylogenetic analysis of the MMBL domains present in eukaryotic and prokaryotic proteins assigned the putidacin domains to a new bacterial clade within the MMBL-containing protein family . Heterologous expression of the llpA gene also conveyed bacteriocin production to several Pseudomonas fluorescens strains . In addition, we demonstrated that strain BW11M1 and heterologous hosts secrete LlpA into the growth medium without requiring a cleavable signal sequence . Most likely, the mode of action of this lectin-like bacteriocin is different from the modes of action of previously described Pseudomonas bacteriocins .
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