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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




Journal article


Biochim Biophys Acta

Publication Date





260 - 267


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