title: Genetic and phenotypic characterization of the heat shock response in Pseudomonas putida.
abstract: Molecular chaperones function in various important physiological processes. Null mutants of genes for the molecular chaperone ClpB (Hsp104), and those that encode J-domain proteins (DnaJ, CbpA, and DjlA), which may act as Hsp40 co-chaperones of DnaK (Hsp70), were constructed from Pseudomonas putida KT2442 (KT) to elucidate their roles. The KTΔclpB mutant showed the same heat shock response (HSR) as the wild-type, both in terms of heat-shock protein (Hsp) synthesis (other than ClpB) and in hsp gene expression; however, the mutant was quite sensitive to high temperatures and was unable to disaggregate into thermo-mediated protein aggregates, indicating that ClpB is important for cell survival after heat stress and essential for solubilization of protein aggregates. On the other hand, the KTΔdnaJ mutant was temperature-sensitive, and formed more protein aggregates (especially of high molecular weight) upon heat stress than did KT. P. putida CbpA, a probable Hsp, partially substituted the functions of DnaJ in cell growth and solubilization of thermo-mediated protein aggregates, and might be involved in the HSR which was regulated by a fine-tuning system(s) that could sense subtle changes in the ambient temperature and control the levels of σ(32) activity and quantity, as well as the mRNA levels of hsp genes.
authors.affiliation: Graduate School of Life Sciences, Toyo University, Gunma.
authors.forename: Fumihiro
authors.initials: F
authors.lastname: Ito
authors.forename: Takayuki
authors.initials: T
authors.lastname: Tamiya
authors.forename: Iwao
authors.initials: I
authors.lastname: Ohtsu
authors.forename: Makoto
authors.initials: M
authors.lastname: Fujimura
authors.forename: Fumiyasu
authors.initials: F
authors.lastname: Fukumori
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D005838:Genotype; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018869:Heat-Shock Response; D006358:Hot Temperature; D010641:Phenotype; D016958:Pseudomonas putida / Q000235:genetics* / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D006360:Heat-Shock Proteins
keywords: Molecular chaperone; Pseudomonas putida; protein disaggregation