Crystal Structure of a Symmetric Football-Shaped GroEL:GroES2-ATP14 Complex Determined at 3.8 Å Reveals Rearrangement between Two GroEL Rings

The chaperonin GroEL is an essential chaperone that assists in protein folding with the aid of GroES and ATP. GroEL forms a double-ring structure, and both rings can bind GroES in the presence of ATP. Recent progress on the GroEL mechanism has revealed the importance of a symmetric 1:2 GroEL:GroES(2) complex (the football-shaped complex) as a critical intermediate during the functional GroEL cycle. We determined the crystal structure of the football GroEL:GroES(2)-ATP(14) complex from Escherichia coli at 3.8 angstrom, using a GroEL mutant that is extremely defective in ATP hydrolysis. The overall structure of the football complex resembled the GroES-bound GroEL ring of the asymmetric 1:1 GroEL:GroES complex (the bullet complex). However, the two GroES-bound GroEL rings form a modified interface by an similar to 7 degrees rotation about the 7-fold axis. As a result, the inter-ring contacts between the two GroEL rings in the football complex differed from those in the bullet complex. The differences provide a structural basis for the apparently impaired inter-ring negative cooperativity observed in several biochemical analyses. (C) 2014 Elsevier Ltd. All rights reserved.