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J Biol Chem. 2010 Sep 3;285(36):27958-66. doi: 10.1074/jbc.M110.125344. Epub 2010 Jun 23.

Crystal structures of a group II chaperonin reveal the open and closed states associated with the protein folding cycle.

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Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.


Chaperonins are large protein complexes consisting of two stacked multisubunit rings, which open and close in an ATP-dependent manner to create a protected environment for protein folding. Here, we describe the first crystal structure of a group II chaperonin in an open conformation. We have obtained structures of the archaeal chaperonin from Methanococcus maripaludis in both a peptide acceptor (open) state and a protein folding (closed) state. In contrast with group I chaperonins, in which the equatorial domains share a similar conformation between the open and closed states and the largest motions occurs at the intermediate and apical domains, the three domains of the archaeal chaperonin subunit reorient as a single rigid body. The large rotation observed from the open state to the closed state results in a 65% decrease of the folding chamber volume and creates a highly hydrophilic surface inside the cage. These results suggest a completely distinct closing mechanism in the group II chaperonins as compared with the group I chaperonins.

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