title: Both the N- and C-terminal chaperone sites of Hsp90 participate in protein refolding.
abstract: Hsp90 is able to bind partially unfolded firefly luciferase and maintain it in a refoldable state; the subsequent successive action of the 20S proteasome activator PA28, Hsc70 and Hsp40 enables its refolding. Hsp90 possesses two chaperone sites in the N- and C-terminal domains that prevent the aggregation of denatured proteins. Here we show that both chaperone sites of Hsp90 are effective not only in capturing thermally denatured luciferase, but also in holding it in a state prerequisite for the successful refolding process mediated by PA28, Hsc70 and Hsp40. In contrast, the heat-induced activity of Hsp90 to bind chemically denature dihydrofolate reductase efficiently and prevent its rapid spontaneous refolding was detected in the N-terminal site of Hsp90 only, while the C-terminal site was without effect. Thus it is most likely that both the N- and C-terminal chaperone sites may contribute to Hsp90 function as holder chaperones, however, in a significantly distinct manner.
authors: Department of Biochemistry, Oita Medical University, Oita, Japan. minami@oita-md.ac.jp
authors: M
authors: M
authors: Minami
authors: M
authors: M
authors: Nakamura
authors: Y
authors: Y
authors: Emori
authors: Y
authors: Y
authors: Minami
mesh_terms: D000818:Animals; D001324:Autoantigens; D016227:Benzoquinones; D001665:Binding Sites; D005982:Glutathione Transferase / Q000378:metabolism; D050883:HSC70 Heat-Shock Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry* / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism; D006358:Hot Temperature; D006801:Humans; D047029:Lactams, Macrocyclic; D008027:Light; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D018832:Molecular Chaperones / Q000378:metabolism*; D009124:Muscle Proteins; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D011506:Proteins / Q000378:metabolism; D011809:Quinones / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D012542:Scattering, Radiation; D013696:Temperature; D013762:Tetrahydrofolate Dehydrogenase / Q000378:metabolism; D013997:Time Factors
chemical_list: D001324:Autoantigens; D016227:Benzoquinones; C494647:DNAJB1 protein, human; D050883:HSC70 Heat-Shock Proteins; D050956:HSP40 Heat-Shock Proteins; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; C494371:HSPA8 protein, human; D006360:Heat-Shock Proteins; C494372:Hspa8 protein, mouse; C099558:Ki antigen; D047029:Lactams, Macrocyclic; D018832:Molecular Chaperones; D009124:Muscle Proteins; C085047:PSME1 protein, human; D011506:Proteins; D011809:Quinones; D011994:Recombinant Proteins; D008156:Luciferases; D013762:Tetrahydrofolate Dehydrogenase; D005982:Glutathione Transferase; D046988:Proteasome Endopeptidase Complex; C001277:geldanamycin