title: Myopathy-causing Q147P TPM2 mutation shifts tropomyosin strands further towards the open position and increases the proportion of strong-binding cross-bridges during the ATPase cycle.
abstract: The molecular mechanisms of skeletal muscle dysfunction in congenital myopathies remain unclear. The present study examines the effect of a myopathy-causing mutation Q147P in β-tropomyosin on the position of tropomyosin on troponin-free filaments and on the actin–myosin interaction at different stages of the ATP hydrolysis cycle using the technique of polarized fluorimetry. Wild-type and Q147P recombinant tropomyosins, actin, and myosin subfragment-1 were modified by 5-IAF, 1,5-IAEDANS or FITC-phalloidin, and 1,5-IAEDANS, respectively, and incorporated into single ghost muscle fibers, containing predominantly actin filaments which were free of troponin and tropomyosin. Despite its reduced affinity for actin in co-sedimentation assay, the Q147P mutant incorporates into the muscle fiber. However, compared to wild-type tropomyosin, it locates closer to the center of the actin filament. The mutant tropomyosin increases the proportion of the strong-binding myosin heads and disrupts the co-operation of actin and myosin heads during the ATPase cycle. These changes are likely to underlie the contractile abnormalities caused by this mutation.
authors.affiliation: Laboratory of Mechanisms of Cell Motility, Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., 194064 St Petersburg, Russia.
authors.forename: Olga E
authors.initials: OE
authors.lastname: Karpicheva
authors.affiliation: Laboratory of Mechanisms of Cell Motility, Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Av., 194064 St Petersburg, Russia; Saint Petersburg State University, 7/9 Universitetskaya nab., 199034 St Petersburg, Russia.
authors.forename: Armen O
authors.initials: AO
authors.lastname: Simonyan
authors.affiliation: Saint Petersburg State University, 7/9 Universitetskaya nab., 199034 St Petersburg, Russia.
authors.forename: Nadezhda V
authors.initials: NV
authors.lastname: Kuleva
authors.affiliation: Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, OX3 9DU Oxford, 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 Av., 194064 St Petersburg, Russia. Electronic address: borovikov@incras.ru.
authors.forename: Yurii S
authors.initials: YS
authors.lastname: Borovikov
mesh_terms: D008841:Actin Cytoskeleton / Q000235:genetics / Q000378:metabolism; D000199:Actins / Q000235:genetics / Q000378:metabolism*; D000251:Adenosine Triphosphatases / Q000378:metabolism; D001665:Binding Sites; D006801:Humans; D018485:Muscle Fibers, Skeletal / Q000378:metabolism / Q000473:pathology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000473:pathology; D009135:Muscular Diseases / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D009154:Mutation; D009218:Myosins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D014335:Tropomyosin / Q000235:genetics* / Q000378:metabolism; D014336:Troponin / Q000378:metabolism
chemical_list: D000199:Actins; C518659:TPM2 protein, human; D014335:Tropomyosin; D014336:Troponin; D000251:Adenosine Triphosphatases; D009218:Myosins
keywords: Actin; Congenital myopathy; Ghost muscle fiber; Myosin head; Polarized fluorescence; β-Tropomyosin