Mechanical measurements of single actomyosin motor force.
To elucidate the mechanism of force generation by actomyosin motor, a measuring system was constructed, in which an in vitro motility assay was combined with an optical trapping technique. An actin filament of several micron long was attached to a gelsolin-coated polystyrene bead, and was allowed to interact with a small number (approximately 1/1 micron actin filament) of rabbit skeletal heavy meromyosin (an active subfragment of myosin) molecules bound to a nitrocellulose-coated coverglass. The bead position was determined at 33-ms intervals. We measured the force generation event at relatively low (100-400 nM) ATP concentration so that the occurrence of individual force generation events could be detected with our time resolution. The actin-bound bead held in the optical trap moved in a stepwise manner in the direction of the actin filament only in the presence of ATP. At the trap strength of 0.3 pN/nm, the maximum size of the step was 11 nm, and the maximum force associated with the movement was 3.3 pN.
Miyata
H
H
Department of Physics, Faculty of Science and Technology, Keio University, Yokohama, Japan.
Yoshikawa
H
H
Hakozaki
H
H
Suzuki
N
N
Furuno
T
T
Ikegami
A
A
Kinosita
K
K
Nishizaka
T
T
Ishiwata
S
S
D000199:Actins / Q000502:physiology; D000205:Actomyosin / Q000502:physiology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001696:Biomechanical Phenomena; D055592:Biophysical Phenomena; D001703:Biophysics; D066298:In Vitro Techniques; D008854:Microscopy, Electron; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D015879:Myosin Subfragments / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure; D011487:Protein Conformation; D011817:Rabbits
D000199:Actins; D015879:Myosin Subfragments; D000255:Adenosine Triphosphate; D000205:Actomyosin