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Journal of Biochemistry Advance Access originally published online on January 2, 2008
Journal of Biochemistry 2008 143(4):505-515; 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 Hirai2, Kentaro Noi2, Kunihiro Hongo1,2, Tomohiro Mizobata1,2 and Yasushi Kawata1,2,*

1Department of Biotechnology, Faculty of Engineering; and 2Department 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. Tel: +81 857 31 5271, 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 and luciferase 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 folding assistance ability with ATP-dependent substrate release may provide a detailed look at the potential functional capabilities of archaeal chaperonins.

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

Abbreviations: ANS, 8-anilino-1-naphthalene sulfonic acid; CCT, chaperonin containing t-complex polypeptide; Gdn-HCl, guanidine hydrochloride; GFP, green fluorescent protein; MDH, malate dehydrogenase; Ta-cpn {alpha}, recombinant chaperonin that is comprised of 16 {alpha}-subunits from Thermoplasma acidophilum


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