Searching for kinesin's mechanical amplifier

Kinesin, a microtubule-based motor; and myosin, an actin-based motor, share a similar core structure, indicating that they arose from a common ancesto r. However, kinesin lacks the long lever-arm domain that is believed to dri ve the myosin power stroke. Here, we present evidence that a much smaller r egion of ca. 10-40 amino acids serves as a mechanical element for kinesin m otor proteins. These 'neck regions' are class conserved and have distinct s tructures in plus-end and minus-end-directed kinesin motors. Mutagenesis st udies also indicate that the neck regions are involved in coupling ATP hydr olysis and energy into directional motion along the microtubule. We suggest that the kinesin necks drive motion by undergoing a conformational change in which they detach and re-dock onto the catalytic core during the ATPase cycle. Thus, kinesin and myosin have evolved unique mechanical elements tha t amplify small, nucleotide-dependent conformational changes that occur in their similar catalytic cores.