Activation of ATPase activity of 14S dynein from Tetrahymena cilia by microtubules.

The ATPase activity of 14S dynein was activated by the presence of microtubule-associated-protein-free microtubules. The activation was 2.5-3.5 fold at 10 mg microtubule/ml, and the activity increased further with increasing microtubule concentration. The microtubule-14S-dynein complex, microtubule bundles with 14S dynein, was treated with a zero-length chemical cross-linker, 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC). The ATPase activity of the complex responded to EDC in a biphasic, concentration-dependent manner and, at most, it was enhanced 5-10 fold. The complex treated with EDC was no longer unbundled by addition of ATP, as revealed by electron-microscopic observation. Several ATP analogues, which support in vitro microtubule translocation mediated by 14S dynein, were turned over faster by this mechanochemical enzyme in the presence of microtubules than in their absence. However, some ATP analogues which do not support the translocation were also turned over faster in the presence of microtubules. Thus, microtubule-dynein motility and substrate-turnover activation are not tightly coupled, which indicates that all three major motor systems, actin- heavy-meromyosin, microtubule-kinesin [Shimizu, T., Furusawa, K., Ohashi, S., Toyoshima, Y. Y., Okuno, M., Malik, F. & Vale, R. D. (1991) J. Cell Biol. 112, 1189-1197] and microtubule-dynein, have this characteristic property in common.