Structural and functional insight into the regulation of kinesin-1 by microtubule associated protein MAP7

The microtubule (MT)-associated protein, MAP7 is a required cofactor for kinesin-1 driven transport of intracellular cargoes. Using cryo-electron microscopy and single-molecule imaging, we investigated how MAP7 binds MTs and facilitates kinesin-1 motility. The MT-binding domain (MTBD) of MAP7 bound MTs as an extended α-helix between the protofilament ridge and the site of lateral contact. Unexpectedly, the MTBD partially overlapped with kinesin-1’s binding site and inhibited kinesin-1 motility. However, by tethering kinesin-1 to the MT, the projection domain of MAP7 prevented dissociation of the motor and facilitated its binding to available neighboring sites. The inhibitory effect of the MTBD dominated as MTs became saturated with MAP7. Our results reveal biphasic regulation of kinesin-1 by MAP7 in the context of their competitive binding to MTs.