کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1177705 | 962562 | 2016 | 8 صفحه PDF | دانلود رایگان |
• Despite low affinity in solution, Q147P tropomyosin binds with actin in muscle fiber.
• The mutation shifts tropomyosin strands closer to the center of the actin filament.
• The mutant tropomyosin increases the proportion of the strong-binding myosin heads.
• These structural changes underlie contractile abnormalities at the congenital myopathy.
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.
Journal: Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics - Volume 1864, Issue 3, March 2016, Pages 260–267