title: Characterization of group II chaperonins from an acidothermophilic archaeon Picrophilus torridus.
abstract: Chaperonins are a type of molecular chaperone that assist in the folding of proteins. Group II chaperonins play an important role in the proteostasis in the cytosol of archaea and eukarya. In this study, we expressed, purified, and characterized group II chaperonins from an acidothermophilic archaeon Picrophilus torridus. Two genes exist for group II chaperonins, and both of the gene products assemble to form double-ring complexes similar to other archaeal group II chaperonins. One of the Picrophilus chaperonins, PtoCPNα, was able to refold denatured GFP at 50 °C. As expected, PtoCPNα exhibited an ATP-dependent conformational change that is observed by the change in fluorescence and diffracted X-ray tracking (DXT). In contrast, PtoCPNα lost its protein folding ability at moderate temperatures, becoming unable to interact with unfolded proteins. At lower temperatures, the release rate of the captured GFP from PtoCPNα was accelerated, and the affinity of denatured protein to PtoCPNα was weakened at the lower temperatures. Unexpectedly, in the DXT experiment, the fine motions were enhanced at the lower temperatures. Taken together, the results suggest that the fine tilting motions of the apical domain might correlate with the affinity of group II chaperonins for denatured proteins.
authors.affiliation: Department of Biotechnology and Life Science Tokyo University of Agriculture and Technology Koganei Japan; Research Fellow of Japan Society for the Promotion of Science Chiyoda, Tokyo Japan.
authors.forename: Yohei Y
authors.initials: YY
authors.lastname: Yamamoto
authors.affiliation: Department of Biotechnology and Life Science Tokyo University of Agriculture and Technology Koganei Japan.
authors.forename: Kanako
authors.initials: K
authors.lastname: Tsuchida
authors.affiliation: Instrumentation Analysis Center Tokyo University of Agriculture and Technology Koganei Japan.
authors.forename: Keiichi
authors.initials: K
authors.lastname: Noguchi
authors.affiliation: Department of Integrated Science in Physics and Biology College of Humanities and Sciences Nihon University Setagaya-ku Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Ogawa
authors.affiliation: Japan Synchrotron Radiation Research Institute Sayo Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sekiguchi
authors.affiliation: Graduate School of Frontier Sciences University of Tokyo Kashiwa Japan.
authors.forename: Yuji C
authors.initials: YC
authors.lastname: Sasaki
authors.affiliation: Department of Biotechnology and Life Science Tokyo University of Agriculture and Technology Koganei Japan.
authors.forename: Masafumi
authors.initials: M
authors.lastname: Yohda
keywords: Picrophilus torridus; archaea; chaperone; chaperonin; dynamics; single molecule