The chaperonin GroEL adopts a double-ring structure with various modes of allosteric communication. The simultaneous positive intra-ring and negative inter-ring cooperativities allow alternating functionality of the folding cavities in both protein rings. Mutation of glutamic acid 434 (located at the ring interface), to lysine alters the negative inter-ring cooperativity. The crystal structure of the mutant chaperonin GroELE434K has been determined at low-resolution (4.5 Å) and has been compared to the wild-type GroEL and the allosteric-defective GroELE461K mutant structures. Despite the allosteric-defective behavior of the GroELE434Kmutant, its structure remains strikingly similar to that of the wild-type GroEL.
Key words: Chaperonin, GroEL, cooperativity, twinning, low-resolution refinement.
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