Fig. 2

X-ray crystal structures of CPN60β1 oligomers. a The side view of the crystal structure perpendicular to the axis of the oligomeric cylinder (left) and top view parallel to the axis of the oligomeric cylinder (right). Individual subunits are designated by different colors. Estimated structural dimensions are indicated. b Comparison of the structures of CPN60β1 oligomer versus GroEL. Position of helix H to helix I is colored in pink in CPN60β1 and yellow in GroEL (upper images of each chaperonin alone and lower left merged image of both chaperonins) to show the size of the central cavity. The diameter of the central cavities is indicated in the top images. The position of helix K to helix L is highlighted with pink in CPN60β1 and yellow in GroEL (lower right merged image of both chaperonins). c The bottom view of E1 and E2 domains from the upper single ring. CPN60β1 is colored in pink and GroEL in yellow. d Numbers of amino acids involved in the inter- and intra-ring contacts within one subunit. A contact was defined as an atomic distance between two amino acids of less than 4 Å. The number of amino acids in each domain is shown; 14 amino acids (shown in parentheses) in the equatorial domain are involved in inter-ring contacts. e Position of E209 in different conformations. The GroEL apo state, the CPN60β1 apo state, and GroEL-ADP state are colored in yellow, pink, and orange, respectively