The Pathway of ATP Hydrolysis by Dynein KINETICS OF

The kinetics of ATP binding and hydrolysis (formation of acid-labile phosphate) by the Tetrahymena 30 S dynein ATPase has been measured by chemical quench flow methods. The amplitude of the ATP-binding transient gave a molecular weight per ATP-binding site of approximately 750,000, suggesting nearly 3 ATP binding sites12 million M, dynein molecule (Johnson, K. A., and Wall, J. S . (1983) J. Cell Biol. 96, 669-678). ATP binding occurred at the rate predicted from the apparent second order ate constant of 4.7 X lo6 M” s” measured by analysis of the ATP-induced dissociation of the microtubule-dynein complex (Porter, M. E., and Johnson, K. A. (1983) J. Biol. Chem. 258,6582-6587). Hydrolysis was slower than binding and occurred at a rate of 55 s-’, at 30 and 50 PM ATP. The rate limiting step for steady state turnover (product release) occurred with a rate constant of 8 s”. These data show that the first two steps of the pathway of coupling ATP hydrolysis to the microtubule-dynein cross-bridge cycle are the same as those described by Lymn and Taylor for actomyosin (Lymn, R. W., and Taylor, E. W. (1971) Biochemistry 10, 4617-4624). Namely, ATP binding induces the very rapid dissociation of dynein from the microtubule and ATP hydrolysis occurs more slowly following dissociation. Moreover, in spite of rather gross structural differences, the kinetic constants for dynein and myosin are quite similar.