A single mutation at the catalytic site of TF1-α3β3γ complex switches the kinetics of ATP hydrolysis from negative to positive cooperativity

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Abstract
Previously, we reported the substitution of Tyr341 of the F1-ATPase β subunit from a thermophilic Bacillus strain PS3 with leucine, cysteine, or alanine (M. Odaka et al. J. Biochem., 115 (1994) 789–796). These mutations resulted in a great decrease in the affinity of the isolated β subunit for ATP-Mg and an increase in the apparent K m of the α3β3γ complex in ATP hydrolysis when examined above 0.1 mM ATP. Here, we examined the ATPase activity of the mutant complexes in a wide range of ATP concentration and found that the mutants exhibited apparent positive cooperativity in ATP hydrolysis. This is the first clear demonstration that a single mutation in the catalytic sites converts the kinetics from apparent negative cooperativity in the wild-type α3β3γ complex to apparent positive cooperativity. The conversion of apparent cooperativity could be explained in terms of a simple kinetic scheme based on the binding change model proposed by Boyer.

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