Allosteric inhibition of kinesin-5 modulates its processive directional motility

Abstract

Small-molecule inhibitors of kinesin-5 (refs. 1–3), a protein essential for eukaryotic cell division⁴, represent alternatives to antimitotic agents that target tubulin^5,6. While tubulin is needed for multiple intracellular processes, the known functions of kinesin-5 are limited to dividing cells, making it likely that kinesin-5 inhibitors would have fewer side effects than do tubulin-targeting drugs. Kinesin-5 inhibitors, such as monastrol¹, act through poorly understood allosteric mechanisms, not competing with ATP binding^7,8. Moreover, the microscopic mechanism of full-length kinesin-5 motility is not known. Here we characterize the motile properties and allosteric inhibition of Eg5, a vertebrate kinesin-5, using a GFP fusion protein in single-molecule fluorescence assays⁹. We find that Eg5 is a processive kinesin whose motility includes, in addition to ATP-dependent directional motion, a diffusive component not requiring ATP hydrolysis. Monastrol suppresses the directional processive motility of microtubule-bound Eg5. These data on Eg5's allosteric inhibition will impact these inhibitors' use as probes and development as chemotherapeutic agents.