title: A tricistronic heat shock operon is important for stress tolerance of Pseudomonas putida and conserved in many environmental bacteria.
abstract: Small heat shock proteins (sHsps) including the well-studied IbpA protein from Escherichia coli are molecular chaperones that bind to non-native proteins and prevent them from aggregation. We discovered an entirely unexplored tricistronic small heat shock gene cluster in Pseudomonas putida. The genes pp3314, pp3313 and pp3312 (renamed to hspX, hspY and hspZ respectively) are transcribed in a single transcript. In addition to σ(32) -dependent transcriptional control, translation of the first and second gene of the operon is controlled by RNA thermometers with novel architectures. Biochemical analysis of HspY, HspZ and P. putida IbpA demonstrated that they assemble into homo-oligomers of different sizes whose quaternary structures alter in a temperature-dependent manner. IbpA and HspY are able to prevent the model substrate citrate synthase from thermal aggregation in vitro. Increased stress sensitivity of a P. putida strain lacking HspX, HspY and HspZ revealed an important role of these sHsps in stress adaptation. The hspXYZ operon is conserved among metabolically related bacteria that live in hostile environments including polluted soils. This heat shock operon might act as a protective system to promote survival in such ecological niches.
authors.affiliation: Microbial Biology, Ruhr University Bochum, Bochum, Germany.
authors.forename: Stefanie S
authors.initials: SS
authors.lastname: Krajewski
authors.forename: Matthias
authors.initials: M
authors.lastname: Joswig
authors.forename: Miriam
authors.initials: M
authors.lastname: Nagel
authors.forename: Franz
authors.initials: F
authors.lastname: Narberhaus
mesh_terms: D020121:5' Untranslated Regions; D000222:Adaptation, Physiological; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D018869:Heat-Shock Response; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009876:Operon; D020836:Protein Structure, Quaternary; D016958:Pseudomonas putida / Q000235:genetics* / Q000378:metabolism; D012329:RNA, Bacterial / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D020121:5' Untranslated Regions; D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger