MICROTUBULE INTERACTION SITE OF THE KINESIN MOTOR

Kinesin and myosin are motor proteins that share a common structural c ore and bind to microtubules and actin filaments, respectively. While the actomyosin interface has been well studied, the location of the mi crotubule-binding site on kinesin has not been identified. Using alani ne-scanning mutagenesis, we have found that microtubule-interacting ki nesin residues are located in three loops that cluster in a patch on t he motor surface. The critical residues are primarily positively charg ed, which is consistent with a primarily electrostatic interaction wit h the negatively charged tubulin molecule. The core of the microtubule -binding interface resides in a highly conserved loop and helix (L12/a lpha 5) that corresponds topologically to the major actin-binding doma in of myosin. Thus, kinesin and myosin have developed distinct polymer -binding domains in a similar region with respect to their common cata lytic cores.