Cooperativity in ATP hydrolysis by GroEL is increased by GroES.

The kinetics of ATP hydrolysis by the 'molecular chaperone' GroEL and the inhibition of this hydrolysis by GroES have been studied in more detail. It is shown that the hydrolysis of ATP by GroEL is cooperative with respect to ATP with a Hill coefficient of 1.86 (+/- 0.13). In the presence of GroES, there is an increase in the degree of cooperativity with a Hill coefficient of 3.01 (+/- 0.18). The observed cooperativity is not due to dissociation of the GroEL oligomer into smaller units but more probably involves structural changes within the GroEL oligomer.