Regulation of dynein-driven microtubule sliding by the radial spokes in flagella.

The regulation of microtubule sliding in flagellar axonemes was studied with the use of Chlamydomonas mutants and in vitro assays. Microtubule sliding velocities were diminished in axonemes from mutant cells missing radial spoke structures but could be restored upon reconstitution with dynein from axonemes with wild-type radial spokes. These experiments demonstrate that the radial spokes activate dynein's microtubule sliding activity.