title: Temperature-dependent regulation of Thermus thermophilus DnaK/DnaJ chaperones by DafA protein.
abstract: DafA, a unique 8-kDa protein found in Thermus thermophilus, assembles the chaperones DnaK and DnaJ to produce a DnaK(3)-DnaJ(3)-DafA(3) complex (KJA complex). Although, it is known that DafA is denatured irreversibly at nonphysiological 89 degrees C and the KJA complex dissociates into fully active DnaK and DnaJ, the function of the KJA complex is not fully understood. In this article, we report that the reversible dissociation of the KJA complex occurs in a temperature-dependent manner even below physiological 75 degrees C and that excess DafA completely inhibits the chaperone activities of the DnaK system. The inhibited activities are not rescued by supplementing DnaK or DnaJ. The results indicate that DafA inhibits the chaperone activities of both DnaK and DnaJ by forming the KJA complex and can act as a thermosensor under both heat stress and optimal growth conditions.
authors.affiliation: Department of Biology, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Kobe 658-8501, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Mizutani
authors.forename: Shohei
authors.initials: S
authors.lastname: Nemoto
authors.forename: Masasuke
authors.initials: M
authors.lastname: Yoshida
authors.forename: Yo-Hei
authors.initials: YH
authors.lastname: Watanabe
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002950:Citrate (si)-Synthase / Q000378:metabolism; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits; D013696:Temperature; D016963:Thermus thermophilus / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D018832:Molecular Chaperones; D021122:Protein Subunits; D000255:Adenosine Triphosphate; D002950:Citrate (si)-Synthase