title: Functional characterization of the recombinant group II chaperonin alpha from Thermoplasma acidophilum.
abstract: The functional characteristics of group II chaperonins, especially those from archaea, have not been elucidated extensively. Here, we performed a detailed functional characterization of recombinant chaperonin alpha subunits (16-mer) (Ta-cpn alpha) from the thermophilic archaea Thermoplasma acidophilum as a model protein of archaeal group II chaperonins. Recombinant Ta-cpn alpha formed an oligomeric ring structure similar to that of native protein, and displayed an ATP hydrolysis activity (optimal temperature: 60 degrees C) in the presence of either magnesium, manganese or cobalt ions. Ta-cpn alpha was able to bind refolding intermediates of Thermus MDH and GFP in the absence of ATP, and to promote the refolding of Thermus MDH at 50 degrees C in the presence of Mg2+-, Mn2+-, or Co2+-ATP. Ta-cpn alpha also prevented thermal aggregation of rhodanese and luciferase at 50 degrees C. Interestingly, Ta-cpn alpha in the presence of Mn2+ ion showed an increased hydrophobicity, which correlated with an increased efficiency in substrate protein binding. Our finding that Ta-cpn alpha chaperonin system displays folding assistance ability with ATP-dependent substrate release may provide a detailed look at the potential functional capabilities of archaeal chaperonins.
authors.affiliation: Department of Biomedical Science, Institute of Regenerative Medicine and Biofunction, Graduate School of Medical Science, Tottori University, Tottori, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Hirai
authors.forename: Kentaro
authors.initials: K
authors.lastname: Noi
authors.forename: Kunihiro
authors.initials: K
authors.lastname: Hongo
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Mizobata
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Kawata
mesh_terms: D018833:Chaperonins / Q000737:chemistry / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008970:Molecular Weight; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013822:Thermoplasma / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D018833:Chaperonins