Влияние мутаций Arg91Gly и Glu139del в бета-тропомиозине, связанных с наследственной миопатией скелетных мышц человека, на актин-миозиновое взаимодействие

The structural changes in proteins of the contractile apparatus of muscle fibre and the violation of their function due to the point mutations in these proteins can be a cause of many hereditary diseases of the human muscular tissue. One of such diseases are cap-myopathy and distal arthrogryposis, which may be associated with tropomyosin mutations. The deletion of glutamic acid residue at position 139 of b-tropomyosin leads to the development of cap-myopathy, and the replacement of arginine at position 91 with glycine in this protein is linked to distal arthrogryposis. In order to understand how the Arg91Gly 0 Glu139del mutations disrupt the coordinated work of the contractile system of muscle fibres, recombinant b-tropomyosins of the wild type and mutant were overexpressed and were incorporated into the thin filaments of ghost muscle fibre. The fluorescent probes of 1,5-IAEDANS or FITC-phalloidin were specifically linked to the Cys707 of the myosin subfragment-1 and the three neighboring actin monomers, respectively. The polarized fluorescence technique was used to study the spatial arrangements of actin and the myosin at modelling of different stages of the ATPase cycle (in the presence of ADP, ATP and in the absence of a nucleotide) at low and high concentration of calcium ions. Both mutations were shown to change the conformational rearrangements of actin and myosin in the ATP hydrolysis cycle that can be caused by the abnormal behavior of the mutant tropomyosins during regulation. The altered work of the contractile system can be one of the causes of muscle weakness in congenital myopathies associated with these mutations.