title: The E117K mutation in β-tropomyosin disturbs concerted conformational changes of actomyosin in muscle fibers.
abstract: The effect of the skeletal myopathy-causing E117K mutation in human β-tropomyosin on actomyosin structure during the ATPase cycle was studied using fluorescent probes bound to actin subdomain 1 and the myosin head. Multistep changes in flexural rigidity of actin filament and in spatial arrangement of actin subdomain 1 and myosin SH1 helix in troponin-free ghost muscle fibers were revealed. During the ATPase cycle E117K tropomyosin inhibited the rotation of subdomain 1 by 46% and the tilt of the SH1 helix by 49% compared with wild-type. At strong-binding stages the proportion of strong binding sub-states in the actomyosin population is decreased by the mutation. At weak-binding stages abnormally high numbers of switched-on actin monomers were observed, thus indicating a disturbance in concerted conformational changes of actomyosin. These structural alterations are likely to underlie the contractile deficit observed with this mutation.
authors.affiliation: Laboratory of Mechanisms of Cell Motility, Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia.
authors.forename: Olga E
authors.initials: OE
authors.lastname: Karpicheva
authors.affiliation: Department of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, UK.
authors.forename: Charles S
authors.initials: CS
authors.lastname: Redwood
authors.affiliation: Laboratory of Mechanisms of Cell Motility, Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia. Electronic address: borovikov@incras.ru.
authors.forename: Yurii S
authors.initials: YS
authors.lastname: Borovikov
mesh_terms: D000199:Actins / Q000378:metabolism; D000205:Actomyosin / Q000737:chemistry* / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D006801:Humans; D018485:Muscle Fibers, Skeletal / Q000378:metabolism*; D009154:Mutation; D011487:Protein Conformation; D011817:Rabbits; D014335:Tropomyosin / Q000235:genetics* / Q000378:metabolism
chemical_list: D000199:Actins; D014335:Tropomyosin; D000205:Actomyosin; D000251:Adenosine Triphosphatases
keywords: ATPase cycle; Conformational change; Congenital myopathy; β-Tropomyosin