title: Light chain-dependent regulation of Kinesin's interaction with microtubules.
abstract: We have investigated the mechanism by which conventional kinesin is prevented from binding to microtubules (MTs) when not transporting cargo. Kinesin heavy chain (HC) was expressed in COS cells either alone or with kinesin light chain (LC). Immunofluorescence microscopy and MT cosedimentation experiments demonstrate that the binding of HC to MTs is inhibited by coexpression of LC. Association between the chains involves the LC NH2-terminal domain, including the heptad repeats, and requires a region of HC that includes the conserved region of the stalk domain and the NH2 terminus of the tail domain. Inhibition of MT binding requires in addition the COOH-terminal 64 amino acids of HC. Interaction between the tail and the motor domains of HC is supported by sedimentation experiments that indicate that kinesin is in a folded conformation. A pH shift from 7.2 to 6.8 releases inhibition of kinesin without changing its sedimentation behavior. Endogenous kinesin in COS cells also shows pH-sensitive inhibition of MT binding. Taken together, our results provide evidence that a function of LC is to keep kinesin in an inactive ground state by inducing an interaction between the tail and motor domains of HC; activation for cargo transport may be triggered by a small conformational change that releases the inhibition of the motor domain for MT binding.
authors.affiliation: Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: K J
authors.initials: KJ
authors.lastname: Verhey
authors.forename: D L
authors.initials: DL
authors.lastname: Lizotte
authors.forename: T
authors.initials: T
authors.lastname: Abramson
authors.forename: L
authors.initials: L
authors.lastname: Barenboim
authors.forename: B J
authors.initials: BJ
authors.lastname: Schnapp
authors.forename: T A
authors.initials: TA
authors.lastname: Rapoport
mesh_terms: D000818:Animals; D000906:Antibodies; D019556:COS Cells; D018076:DNA, Complementary; D017353:Gene Deletion; D015870:Gene Expression / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D016547:Kinesins / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D020409:Molecular Motor Proteins / Q000378:metabolism; D016296:Mutagenesis / Q000502:physiology; D018994:Myosin Light Chains / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism
chemical_list: D000906:Antibodies; D018076:DNA, Complementary; D020409:Molecular Motor Proteins; D018994:Myosin Light Chains; D014404:Tubulin; D016547:Kinesins