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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.

Original publication

DOI

10.1016/j.bbapap.2015.12.004

Type

Journal article

Journal

Biochim Biophys Acta

Publication Date

03/2016

Volume

1864

Pages

260 - 267

Keywords

Actin, Congenital myopathy, Ghost muscle fiber, Myosin head, Polarized fluorescence, β-Tropomyosin, Actin Cytoskeleton, Actins, Adenosine Triphosphatases, Binding Sites, Humans, Muscle Fibers, Skeletal, Muscle, Skeletal, Muscular Diseases, Mutation, Myosins, Protein Binding, Tropomyosin, Troponin