A kinetic study of the kinesin ATPase

The mechanism of kinesin ATPase has been investigated by transient state kinetic analysis. The results satisfy the scheme [formula: see text] where T, D, and P(i) refer to nucleotide tri- and diphosphate and inorganic phosphate, respectively. The nucleotide-binding steps were measured by the fluorescence enhancement of mant (2'-(3')-O-(N-methylanthraniloyl)-ATP and mant-ADP. The initial rapid equilibrium binding steps (1) and (6) are followed by isomerizations (k2 = 170 +/- 30 s-1 at 20 degrees C, k-5 greater than 100 s-1). The increase in fluorescence is 20-25% larger for K.T** than K.D*. The rate constant of the hydrolysis step k3 is 6-7 s-1. The fluorescence decreases after formation of K.T** at a rate of 7-10 s-1. This change could occur in step 3 or in step 4 if k4 much greater than k3. The value of k4 is larger than 0.1 s-1. The steady state rate is 0.003 s-1 which agrees with the rate of ADP dissociation (k5). Step 5 is rate limiting in the scheme in agreement with the conclusion of Hackney (Hackney, D. D. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 6314-6318) that ADP dissociation is the rate-limiting step.