Temperature-dependent regulation of Thermus thermophilus DnaK/DnaJ chaperones by DafA protein

• Published in: Genes to cells : devoted to molecular & cellular mechanisms 2009-12, Vol.14 (12), p.1405-1413
• Main Authors: Mizutani, Tadashi, Nemoto, Shohei, Yoshida, Masasuke, Watanabe, Yo-hei
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Citrate (si)-Synthase - metabolism; Molecular Chaperones - genetics; Molecular Chaperones - metabolism; Protein Subunits; Temperature; Thermus thermophilus - genetics; Thermus thermophilus - growth & development; Thermus thermophilus - metabolism
• ISSN: 1356-9597; 1365-2443
• DOI: 10.1111/j.1365-2443.2009.01357.x

DafA, a unique 8-kDa protein found in Thermus thermophilus, assembles the chaperones DnaK and DnaJ to produce a DnaK₃-DnaJ₃-DafA₃ complex (KJA complex). Although, it is known that DafA is denatured irreversibly at nonphysiological 89 °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 °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.