title: Switch movements and the myosin crossbridge stroke.
abstract: The myosin II motor from Dictyostelium discoideum has been engineered to contain single tryptophan residues at strategic locations to probe movements of switch 1 and switch 2. The tryptophan residue at W501 probes movement of the relay helix and indirectly reports on switch 2 movement. This probe suggests that there is an equilibrium between the switch 2 open- and closed-states when the gamma-phosphate position is occupied. Actin does not appear to greatly affect this equilibrium directly, but has indirect influence via switch 1. The latter region has been probed by introducing tryptophan residues at positions 239 and 242. The kinetics of the actomyosin ATPase in solution is discussed with respect to recent crossbridge models based on high-resolution crystal structures.
authors.affiliation: Department of Biochemistry, Eötvös Loránd University, Pázmány Péter sétány 1/C, Hungary.
authors.forename: András
authors.initials: A
authors.lastname: Málnási-Csizmadia
authors.forename: Jane L
authors.initials: JL
authors.lastname: Dickens
authors.forename: Wei
authors.initials: W
authors.lastname: Zeng
authors.forename: Clive R
authors.initials: CR
authors.lastname: Bagshaw
mesh_terms: D000199:Actins / Q000737:chemistry / Q000502:physiology; D000818:Animals; D007700:Kinetics; D009068:Movement / Q000502:physiology*; D018482:Muscle, Skeletal / Q000737:chemistry / Q000502:physiology; D015879:Myosin Subfragments / Q000737:chemistry / Q000502:physiology* / Q000648:ultrastructure; D013997:Time Factors; D014364:Tryptophan / Q000737:chemistry / Q000502:physiology
chemical_list: D000199:Actins; D015879:Myosin Subfragments; D014364:Tryptophan