title: Defense against protein carbonylation by DnaK/DnaJ and proteases of the heat shock regulon.
abstract: Protein carbonylation is an irreversible oxidative modification that increases during organism aging and bacterial growth arrest. We analyzed whether the heat shock regulon has a role in defending Escherichia coli cells against this deleterious modification upon entry into stationary phase. Providing the cell with ectopically elevated levels of the heat shock transcription factor, sigma32, effectively reduced stasis-induced carbonylation. Separate overproduction of the major chaperone systems, DnaK/DnaJ and GroEL/GroES, established that the former of these is more important in counteracting protein carbonylation. Deletion of the heat shock proteases Lon and HslVU enhanced carbonylation whereas a clpP deletion alone had no effect. However, ClpP appears to have a role in reducing protein carbonyls in cells lacking Lon and HslVU. Proteomic immunodetection of carbonylated proteins in the wild-type, lon, and hslVU strains demonstrated that the same spectrum of proteins displayed a higher load of carbonyl groups in the lon and hslVU mutants. These proteins included the beta-subunit of RNA polymerase, elongation factors Tu and G, the E1 subunit of the pyruvate dehydrogenase complex, isocitrate dehydrogenase, 6-phosphogluconate dehydrogenase, and serine hydroxymethyltranferase.
authors.affiliation: Department of Cell and Molecular Biology, Microbiology, Medicinaregatan 9C, 413 90 Göteborg, Sweden.
authors.forename: Asa
authors.initials: A
authors.lastname: Fredriksson
authors.forename: Manuel
authors.initials: M
authors.lastname: Ballesteros
authors.forename: Sam
authors.initials: S
authors.lastname: Dukan
authors.forename: Thomas
authors.initials: T
authors.lastname: Nyström
mesh_terms: D002453:Cell Cycle / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000502:physiology; D006360:Heat-Shock Proteins / Q000235:genetics / Q000502:physiology*; D018832:Molecular Chaperones / Q000502:physiology; D009154:Mutation; D018384:Oxidative Stress; D010447:Peptide Hydrolases / Q000235:genetics / Q000502:physiology*; D011489:Protein Denaturation; D018085:Regulon; D013997:Time Factors
chemical_list: C494635:DnaJ protein, E coli; D029968:Escherichia coli Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D010447:Peptide Hydrolases; C063842:dnaK protein, E coli