Visualizing a new binding site of ncd-motor domain on tubulin

Ncd is a microtubule minus-end directed motor of the kinesin superfamily. P reviously it has been shown that ncd and kinesin motor domains share the sa me major binding site on microtubules. sere we report a three-dimensional E M reconstruction of negatively stained two-dimensional Zn-induced tubulin c rystal sheets (Zn-sheets) decorated with the ncd motor domain at a resoluti on of 16 Angstrom This work has revealed a second specific binding site for the ncd motor domain. The motor binding site on the tubulin Zn-sheets span s both alpha and beta tubulin subunits. This binding site is located at a p osition different from the previously identified ncd binding site on microt ubules and may play a role in motor function. (C) 1999 Academic Press.