title: Electron microscopic evidence for the myosin head lever arm mechanism in hydrated myosin filaments using the gas environmental chamber.
abstract: Muscle contraction results from an attachment-detachment cycle between the myosin heads extending from myosin filaments and the sites on actin filaments. The myosin head first attaches to actin together with the products of ATP hydrolysis, performs a power stroke associated with release of hydrolysis products, and detaches from actin upon binding with new ATP. The detached myosin head then hydrolyses ATP, and performs a recovery stroke to restore its initial position. The strokes have been suggested to result from rotation of the lever arm domain around the converter domain, while the catalytic domain remains rigid. To ascertain the validity of the lever arm hypothesis in muscle, we recorded ATP-induced movement at different regions within individual myosin heads in hydrated myosin filaments, using the gas environmental chamber attached to the electron microscope. The myosin head were position-marked with gold particles using three different site-directed antibodies. The amplitude of ATP-induced movement at the actin binding site in the catalytic domain was similar to that at the boundary between the catalytic and converter domains, but was definitely larger than that at the regulatory light chain in the lever arm domain. These results are consistent with the myosin head lever arm mechanism in muscle contraction if some assumptions are made.
authors.affiliation: Department of Applied Physics, Tokyo University of Agriculture and Technology, Koganeishi, Tokyo184-8588, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Minoda
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Okabe
authors.forename: Yuhri
authors.initials: Y
authors.lastname: Inayoshi
authors.forename: Takuya
authors.initials: T
authors.lastname: Miyakawa
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Miyauchi
authors.forename: Masaru
authors.initials: M
authors.lastname: Tanokura
authors.forename: Eisaku
authors.initials: E
authors.lastname: Katayama
authors.forename: Takeyuki
authors.initials: T
authors.lastname: Wakabayashi
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Akimoto
authors.forename: Haruo
authors.initials: H
authors.lastname: Sugi
mesh_terms: D000255:Adenosine Triphosphate / Q000737:chemistry; D000818:Animals; D008854:Microscopy, Electron; D009119:Muscle Contraction; D015879:Myosin Subfragments / Q000737:chemistry* / Q000502:physiology*; D011487:Protein Conformation; D011817:Rabbits
chemical_list: D015879:Myosin Subfragments; D000255:Adenosine Triphosphate