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Journal of Biochemistry Advance Access published online on January 2, 2008
Journal of Biochemistry, doi:10.1093/jb/mvm241
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© 2008 The Japanese Biochemical Society

Functional characterization of the recombinant group II chaperonin {alpha} from Thermoplasma acidophilum

Hidenori Hirai, Kentaro Noi, Kunihiro Hongo, Tomohiro Mizobata and Yasushi Kawata*

Department of Biotechnology, Faculty of Engineering, and Department of Biomedical Science, Institute of Regenerative Medicine and Biofunction, Graduate School of Medical Science, Tottori University, Tottori 680-8552, Japan

*To whom correspondence should be addressed: Dr. Yasushi Kawata: Department of Biotechnology, Faculty of Engineering, Tottori University Koyama-Minami, Tottori 680-8552, Japan, Tel/Fax: +81-857-31-5271, E-mail: kawata{at}bio.tottori-u.ac.jp

Received November 14, 2007; Accepted December 18, 2007


  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°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°C in the presence of Mg2+-, Mn2+-, or Co2+-ATP. Ta-cpn {alpha} also prevented thermal aggregation of rhodanese at 50°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 a folding assistance ability with ATP-dependent substrate release may provide a detailed look at the potential functional capabilities of archaeal chaperonins.

Key Words: archaea chaperonin, chaperonin activity, metal ion, protein folding, Thermoplasma acidophilum


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