title: Myosin-Va binds to and mechanochemically couples microtubules to actin filaments.
abstract: Myosin-Va was identified as a microtubule binding protein by cosedimentation analysis in the presence of microtubules. Native myosin-Va purified from chick brain, as well as the expressed globular tail domain of this myosin, but not head domain bound to microtubule-associated protein-free microtubules. Binding of myosin-Va to microtubules was saturable and of moderately high affinity (approximately 1:24 Myosin-Va:tubulin; Kd = 70 nM). Myosin-Va may bind to microtubules via its tail domain because microtubule-bound myosin-Va retained the ability to bind actin filaments resulting in the formation of cross-linked gels of microtubules and actin, as assessed by fluorescence and electron microscopy. In low Ca2+, ATP addition induced dissolution of these gels, but not release of myosin-Va from MTs. However, in 10 microM Ca2+, ATP addition resulted in the contraction of the gels into aster-like arrays. These results demonstrate that myosin-Va is a microtubule binding protein that cross-links and mechanochemically couples microtubules to actin filaments.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: Tracy T
authors.initials: TT
authors.lastname: Cao
authors.forename: Wakam
authors.initials: W
authors.lastname: Chang
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Masters
authors.forename: Mark S
authors.initials: MS
authors.lastname: Mooseker
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002645:Chickens / Q000378:metabolism*; D007313:Insecta / Q000821:virology; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000378:metabolism*; D009119:Muscle Contraction / Q000502:physiology*; D018995:Myosin Heavy Chains / Q000378:metabolism*; D024701:Myosin Type V / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary / Q000502:physiology
chemical_list: D000255:Adenosine Triphosphate; D024701:Myosin Type V; D018995:Myosin Heavy Chains; D002118:Calcium