Inter-ring communication is disrupted in the GroEL mutant Arg13->Gly; Ala126->Val with known crystal structure

The crystal structures of the chaperonin GroEL Arg13 --> Gly; Ala126 --> Val double mutant, without and in complex with ATP gamma S, have been determined at atomic resolution. Here, we show that the double mutation Arg13 --> Gly; Ala126 --> Val disrupts negative co-operativity between GroEL rings, with respect to ATP, but has little effect on the positive co-operativity within each ring. Our results help to explain why the double mutation facilitated the crystallization of GroEL and why breaking of dyad symmetry between rings is not observed in crystal structures of this mutant. Our results may also help to explain why the observed structural differences between the GroEL double mutant and its ATP gamma S-bound form are small. (C) 1996 Academic Press Limited