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The effect of Arg167His, Arg167Gly and Lys168Glu mutations in TPM1 gene on position of tropomyosin and spatial organization of myosin heads and actin during the ATPase cycleтезисы доклада
- Авторы: Avrova S.V., Rysev N.A., Karpicheva O.E., Borys D., Moraczewska J., Borovikov Y.S.
- Сборник: In Abstracts of International Symposium «Biological Motility: New facts and hypotheses», Pushchino, Russia
- Тезисы
- Год издания: 2016
- Первая страница: 11
- Последняя страница: 12
- Аннотация: Tropomyosin (TM) changes its azimuthal position on F-actin, exposing in the presence of Ca2+ (closed position) or blocking in the absence of Ca2+ (blocked position) myosin binding sites on actin, thereby controlling myosin interaction with actin and contractility [Lehman et al., 2013, J. Muscle Res. Cell Motil. 34: 155–163]. The positions that TM strands take in both thin filaments and troponin-free actin filaments during the ATPase cycle were found to be correlated with the number of the switched on actin subunits and the amount of the strongly bound myosin heads [Borovikiov et al., 2009, Biochim Biophys Acta, 1794: 985–994]. It was shown that the shift of TM to the inner domain of actin resulted in an in-creased amount of both switched on F-actin subunits and myosin heads strongly bound to F-actin; the movement of TM to the outer domain of actin led to a de-creased proportion of these subunits and the strongly bound myosin heads. This relationship may be uncoupled by point mutations in α- and β-TMs [Rysev et al., 2012, Biochim. Biophys. Acta, 1824: 366–373; Borovikov et al., 2015, Arch. Bio-chem. Biophys. 577-578: 11–23; Karpicheva et al., 2016, Biochim. Biophys. Acta, 2016, 1864: 260–267]. There is evidence that myopathies in skeletal muscle may be provoked by mutations in the TPM1, TPM2 and TPM3 genes, which may induce contractile dysfunction [Marston et al., 2013, Hum. Mol. Genet. 22: 4978–4987; Marttila et al., 2014, Hum. Mutat. 35: 779–790]. In particular, point mutations in TPM3 gene leading to the Arg167His, Arg167Gly and Lys168Glu replacements have been associated with congenital fiber type disproportion and cap disease. Functional effects of these mutations in TPM1 gene were examined in biochemical assays using recombinant tropomyosin mutants and native proteins isolated from skeletal muscle [Robaszkiewicz et al., 2012, Biochim. Biophys. Acta 1822: 1562–1569]. The work indicated that all these mutations decreased the affinity of tropomyosin for actin, and suppressed the Ca2+-induced activation and the ATPase activity of myosin [Robaszkiewicz et al., 2015, Biochem. Biophys. Acta 1854: 381–390]. However it is unclear how these mutations affect the behaviour of TM strands and the response of actin and myosin during the ATPase cycle when troponin is absent. To investigate how the Arg167His, Arg167Gly and Lys168Glu mutations in tropomyosin isoform Tpm 1.1 (TM) affect the relocation of TM strands and the conformational state of the myosin heads and actin during the ATPase cycle, we labelled the recombinant wild-type and mutant TMs with 5-IAF, S1 with 1,5-IAEDANS and F-actin with FITC-phalloidin, incorporated them into the ghost muscle fibres and studied polarized fluorescence. It was shown that the Arg167His mutation shifts TM further to the periphery of the filaments (towards the blocked position) and inhibits the switching on of actin monomers and the strong binding of the myosin heads to actin. On the contrary, the Arg167Gly and Arg168Glu mutations shift TM further to the filament centre (towards the open position) and activate strong binding of the myosin heads throughout the ATPase cycle. The data suggest that the reasons for the defective response of the myosin heads and actin during the ATPase cycle that has been observed in troponin-free filaments containing the Lys168Glu, Arg167Gly and Arg167His mutant TMs are that the Arg167His mutation leads to a shift of TM strands towards the blocked position which inhibits the switching of actin monomers on and the formation of the strong binding of myosin to actin, while Lys168Glu and Arg167Gly mutations facilitate stronger myosin binding to actin. These defects can result in muscle weakness observed at congenital fiber type disproportion and cap disease [Lehtokari et al., 2007, Neuromusc. Disord. 17: 433–442; Clarke et al., 2009, Neuromusc. Disord. 19: 348–351]. This work was supported by the Russian Foundation for Basic Research (№ 14-04-00454) and statutory funds to Kazimierz Wielki University.
- Добавил в систему: Карпичева Ольга Евгеньевна