INTERACTION OF MONOMERIC AND DIMERIC KINESIN WITH MICROTUBULES

The binding stoichiometry of kinesin to microtubules was determined us ing several biochemical and biophysical approaches (chemical crosslink ing, binding assays, scanning-transmission electron microscopy (STEM), image reconstruction-and X-ray scattering). The results show that eac h tubulin dimer associates with one kinesin head, irrespective of whet her kinesin occurs in a monomeric or dimeric form in solution. Moreove r, these heads appear to align along the protofilament axis generating a 16 nm periodicity of successive kinesin dimers. This is consistent with a ''tightrope'' model of movement where the first head of the dim er provides a guiding signal for the following one. (C) 1998 Academic Press Limited.