Characterization of archaeal group II chaperonin-ADP-metal fluoride complexes: implications that group II chaperonins operate as a "two-stroke engine".

Abstract	Group II chaperonins, found in Archaea and in the eukaryotic cytosol, act independently of a cofactor corresponding to GroES of group I chaperonins. Instead, the helical protrusion at the tip of the apical domain forms a built-in lid of the central cavity. Although many studies on the lid's conformation have been carried out, the conformation in each step of the ATPase cycle remains obscure. To clarify this issue, we examined the effects of ADP-aluminum fluoride (AlFx) and ADP-beryllium fluoride (BeFx) complexes on alpha-chaperonin from the hyperthermophilic archaeum, Thermococcus sp. strain KS-1. Biochemical assays, electron microscopic observations, and small angle x-ray scattering measurements demonstrate that alpha-chaperonin incubated with ADP and BeFx exists in an asymmetric conformation; one ring is open, and the other is closed. The result indicates that alpha-chaperonin also shares the inherent functional asymmetry of bacterial and eukaryotic cytosolic chaperonins. Most interestingly, addition of ADP and BeFx induced alpha-chaperonin to encapsulate unfolded proteins in the closed ring but did not trigger their folding. Moreover, alpha-chaperonin incubated with ATP and AlFx or BeFx adopted a symmetric closed conformation, and its functional turnover was inhibited. These forms are supposed to be intermediates during the reaction cycle of group II chaperonins.
Authors	Ryo Iizuka, Takao Yoshida, Noriyuki Ishii, Tamotsu Zako, Kazunobu Takahashi, Kosuke Maki, Tomonao Inobe, Kunihiro Kuwajima, Masafumi Yohda
Journal	The Journal of biological chemistry (J Biol Chem) Vol. 280 Issue 48 Pg. 40375-83 (Dec 02 2005) ISSN: 0021-9258 [Print] United States
PMID	16183634 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References	Aluminum Compounds Archaeal Proteins Nucleotides Green Fluorescent Proteins beryllium fluoride Adenosine Diphosphate Tryptophan Peptide Hydrolases Adenosine Triphosphatases Chaperonin Containing TCP-1 Chaperonins Beryllium Fluorides aluminum fluoride
Topics	Adenosine Diphosphate (chemistry) Adenosine Triphosphatases (chemistry) Aluminum Compounds (chemistry) Archaea (metabolism) Archaeal Proteins (chemistry) Beryllium (chemistry) Chaperonin Containing TCP-1 Chaperonins (chemistry) Cytosol (metabolism) Fluorides (chemistry) Green Fluorescent Proteins (chemistry) Microscopy, Electron Models, Biological Nucleotides (chemistry) Peptide Hydrolases (chemistry) Protein Binding Protein Conformation Protein Folding Protein Structure, Tertiary Scattering, Radiation Spectrometry, Fluorescence Temperature Thermococcus (metabolism) Tryptophan (chemistry) X-Rays

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