ATP analogs substituted on the 2-position as substrates for dynein ATPase activity

In contrast to previously studied ATP analogs, the two-substituted ATP analogs, 2-N3 ATP and 2-Cl ATP were good substrates for dynein ATPase. The Vmax for hydrolysis of both analogs was significantly higher than for ATP and the Km for both analogs was comparable to ATP. The higher hydrolytic rate for the analogs might be explained by a faster dissociation rate of the diphosphate product. This interpretation is supported by measurements of the dissociation rate of the inhibitor, vanadate. The estimate dissociation rate of vanadate with the analogs as substrate is approx. 2-fold higher than with ATP as substrate. These data together with previous studies on a variety of ATP analogs suggest that the 6-amino group on adenine is important for recognition by dynein and that the anti-conformation of the adenine, favored by 2-substituents, is the favored conformation of the nucleotide.