title: Three-dimensional structural dynamics of myosin V by single-molecule fluorescence polarization.
abstract: The structural change that generates force and motion in actomyosin motility has been proposed to be tilting of the myosin light chain domain, which serves as a lever arm. Several experimental approaches have provided support for the lever arm hypothesis; however, the extent and timing of tilting motions are not well defined in the motor protein complex of functioning actomyosin. Here we report three-dimensional measurements of the structural dynamics of the light chain domain of brain myosin V using a single-molecule fluorescence polarization technique that determines the orientation of individual protein domains with 20-40-ms time resolution. Single fluorescent calmodulin light chains tilted back and forth between two well-defined angles as the myosin molecule processively translocated along actin. The results provide evidence for lever arm rotation of the calmodulin-binding domain in myosin V, and support a 'hand-over-hand' mechanism for the translocation of double-headed myosin V molecules along actin filaments. The technique is applicable to the study of real-time structural changes in other biological systems.
authors.affiliation: Pennsylvania Muscle Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6083, USA.
authors.forename: Joseph N
authors.initials: JN
authors.lastname: Forkey
authors.forename: Margot E
authors.initials: ME
authors.lastname: Quinlan
authors.forename: M Alexander
authors.initials: MA
authors.lastname: Shaw
authors.forename: John E T
authors.initials: JE
authors.lastname: Corrie
authors.forename: Yale E
authors.initials: YE
authors.lastname: Goldman
mesh_terms: D000199:Actins / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001921:Brain; D002147:Calmodulin / Q000378:metabolism; D002642:Chick Embryo; D005454:Fluorescence Polarization; D007700:Kinetics; D009068:Movement; D024701:Myosin Type V / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011817:Rabbits
chemical_list: D000199:Actins; D002147:Calmodulin; D000255:Adenosine Triphosphate; D024701:Myosin Type V