A single mutation at the catalytic site of TF1-alpha3beta3gamma complex switches the kinetics of ATP hydrolysis from negative to positive cooperativity.
Previously, we reported the substitution of Tyr341 of the F1-ATPase beta 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 beta subunit for ATP-Mg and an increase in the apparent Km of the alpha3beta3gamma 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 alpha3beta3gamma 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.
Muneyuki
E
E
Research Laboratory of Resources Utilization, Tokyo Institute of Technology, Yokohama, Japan.
Odaka
M
M
Yoshida
M
M
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000409:Alanine / Q000737:chemistry; D001665:Binding Sites; D002384:Catalysis; D003545:Cysteine / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D006868:Hydrolysis; D007700:Kinetics; D007930:Leucine / Q000737:chemistry; D008433:Mathematics; D009154:Mutation; D006180:Proton-Translocating ATPases / Q000737:chemistry*; D014443:Tyrosine / Q000737:chemistry*
D014443:Tyrosine; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D007930:Leucine; D003545:Cysteine; D000409:Alanine