INTERACTION OF KINESIN HEAD DOMAINS AND PROCESSIVE MOVEMENT ALONG MICROTUBULES

David Hackney
Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213

Dimers of kinesin head domains are capable processive movement along microtubules as demonstrated by a number of techniques for observing single motor motility. One attractive mechanism for generation of processive movement is the alternating participation of the head domains of a dimer so that one head domain usually remains attached. Thus the individual head domains can detach from the microtubule and reattach to a new site, while the dimer remains tethered to the microtubule by stable attachment of other head. The discovery of half site ADP release by kinesin dimers on binding to the microtubule (Hackney, Proc. Natl. Acad. Sci. 91:6865, 1994) provided direct demonstration that the two heads can be out of phase with regard to their ATPase cycles. Detailed analysis of the coupling of ATPase cycle to the mechanical cycle is complicated by the failure of monomeric head domains to detach from the mimcrotubule during reaction of each ATP molecule (Jiang and Hackney, J. Biol. Chem. 272:5616, 1997). The implications of the properties of the ATPase cycle for coupling to processive movement will be presented.