title: The kinesin-1 motor protein is regulated by a direct interaction of its head and tail.
abstract: Kinesin-1 is a molecular motor protein that transports cargo along microtubules. Inside cells, the vast majority of kinesin-1 is regulated to conserve ATP and to ensure its proper intracellular distribution and coordination with other molecular motors. Regulated kinesin-1 folds in half at a hinge in its coiled-coil stalk. Interactions between coiled-coil regions near the enzymatically active heads at the N terminus and the regulatory tails at the C terminus bring these globular elements in proximity and stabilize the folded conformation. However, it has remained a mystery how kinesin-1's microtubule-stimulated ATPase activity is regulated in this folded conformation. Here, we present evidence for a direct interaction between the kinesin-1 head and tail. We photochemically cross-linked heads and tails and produced an 8-A cryoEM reconstruction of the cross-linked head-tail complex on microtubules. These data demonstrate that a conserved essential regulatory element in the kinesin-1 tail interacts directly and specifically with the enzymatically critical Switch I region of the head. This interaction suggests a mechanism for tail-mediated regulation of the ATPase activity of kinesin-1. In our structure, the tail makes simultaneous contacts with the kinesin-1 head and the microtubule, suggesting the tail may both regulate kinesin-1 in solution and hold it in a paused state with high ADP affinity on microtubules. The interaction of the Switch I region of the kinesin-1 head with the tail is strikingly similar to the interactions of small GTPases with their regulators, indicating that other kinesin motors may share similar regulatory mechanisms.
authors.affiliation: Department of Cell and Molecular Biology, Northwestern University, Chicago, IL 60611, USA.
authors.forename: Kristen A
authors.initials: KA
authors.lastname: Dietrich
authors.forename: Charles V
authors.initials: CV
authors.lastname: Sindelar
authors.forename: Paul D
authors.initials: PD
authors.lastname: Brewer
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Downing
authors.forename: Christine R
authors.initials: CR
authors.lastname: Cremo
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Rice
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D003432:Cross-Linking Reagents / Q000494:pharmacology; D020285:Cryoelectron Microscopy; D006801:Humans; D016547:Kinesins / Q000737:chemistry* / Q000378:metabolism* / Q000528:radiation effects / Q000648:ultrastructure; D008027:Light; D008870:Microtubules / Q000187:drug effects / Q000528:radiation effects; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins / Q000378:metabolism; D011485:Protein Binding / Q000187:drug effects / Q000528:radiation effects; D017434:Protein Structure, Tertiary; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D003432:Cross-Linking Reagents; D000244:Adenosine Diphosphate; D016547:Kinesins; D020559:Monomeric GTP-Binding Proteins