RESUMO
Cardiac myosin binding protein-C (cMyBP-C) located in the C-zone of myocyte sarcomere is involved in the regulation of myocardial contraction. Its N-terminal domains C0, C1, C2, and the m-motif between C1 and C2 can bind to the myosin head and actin of the thin filament and affect the characteristics of their interaction. Measurements using an optical trap showed that the C0-C2 fragment of cMyBP-C increases the interaction time of cardiac myosin with the actin filament, while in an in vitro motility assay, it dose-dependently reduces the sliding velocity of actin filaments. Thus, it was found that the N-terminal part of cMyBP-C affects the kinetics of the myosin cross-bridge.
Assuntos
Actinas , Proteínas de Transporte , Actinas/metabolismo , Proteínas de Transporte/metabolismo , Miosinas/metabolismo , Citoesqueleto de Actina/metabolismo , Miosinas Cardíacas/metabolismo , Ligação Proteica/fisiologia , Miocárdio/metabolismoRESUMO
The review is devoted to tropomyosin (Tpm) - actin-binding protein, which plays a crucial role in the regulation of contraction of skeletal and cardiac muscles. Special attention is paid to myopathies and cardiomyopathies - severe hereditary diseases of skeletal and cardiac muscles associated with point mutations in Tpm genes. The current views on the molecular mechanisms of these diseases and the effects of such mutations on the Tpm structure and functions are considered in detail. Besides, some part of the review is devoted to analysis of the properties of Tpm homodimers and heterodimers with myopathic substitutions of amino acid residues in only one of the two chains of the Tpm dimeric molecule.
Assuntos
Cardiomiopatias/genética , Músculo Esquelético/patologia , Doenças Musculares/genética , Miocárdio/patologia , Mutação Puntual , Tropomiosina/genética , Tropomiosina/metabolismo , Actinas/metabolismo , Animais , Dimerização , Heterozigoto , Humanos , Modelos Moleculares , Contração Muscular/genética , Ligação Proteica , Isoformas de Proteínas , Tropomiosina/químicaRESUMO
Tropomyosin (Tpm) is one of the main regulatory proteins in the myocardium. In some heart pathologies, interchain disulfide crosslinking in the Tpm molecule occurs. In the ventricle, this change in the structural properties of the Tpm molecule affects calcium regulation of the actin-myosin interaction. Using an in vitro motility assay, we found that Tpm crosslinking does not affect the actin-myosin interaction in the atria. We assume that the intramolecular crosslinking of Tpm in the atrium does not play such a crucial role in the pathogenesis of heart failure as it plays in the heart ventricles.
Assuntos
Actinas/metabolismo , Músculo Esquelético/metabolismo , Miocárdio/metabolismo , Miosinas/metabolismo , Tropomiosina/química , Tropomiosina/metabolismo , Actinas/química , Animais , Cálcio/metabolismo , Dissulfetos/química , Dissulfetos/metabolismo , Miosinas/química , Ligação Proteica , CoelhosRESUMO
Tropomyosin plays an important role in the regulation of actin-myosin interaction in striated muscles. Mutations in the tropomyosin gene disrupt actin-myosin interaction and lead to myopathies and cardiomyopathies. Tropomyosin with mutations in the α-chain is expressed in both the myocardium and skeletal muscles. We studied the effect of mutations in the α-chain of tropomyosin related to hypertrophic (D175N and E180G) and dilated cardiomyopathies (E40K and E54K) on calcium regulation of the actin-myosin interaction in skeletal muscles. We analyzed the calcium-dependent sliding velocity of reconstructed thin filaments containing F-actin, troponin, and tropomyosin over myosin surface in an in vitro motility assay. Mutations D175N and E180G in tropomyosin increased the sliding velocity and its calcium sensitivity, while mutation E40K reduced both these parameters. E54K mutation increased the sliding velocity of thin filaments, but did not affect its calcium sensitivity.
Assuntos
Actinas/química , Cálcio/metabolismo , Miosinas/química , Tropomiosina/química , Troponina/química , Actinas/genética , Actinas/metabolismo , Animais , Soluções Tampão , Expressão Gênica , Humanos , Cinética , Músculo Esquelético/química , Músculo Esquelético/fisiologia , Mutação , Miosinas/genética , Miosinas/metabolismo , Ligação Proteica , Coelhos , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Soluções , Tropomiosina/genética , Tropomiosina/metabolismo , Troponina/genética , Troponina/metabolismoRESUMO
We show that the mutations D137L and G126R, which stabilize the central part of the tropomyosin (Tm) molecule, increase both the maximal sliding velocity of the regulated actin filaments in the in vitro motility assay at high Са(2+) concentrations and the Са(2+)-sensitivity of the actin-myosin interaction underlying this sliding. Based on an analysis of the recently published data on the structure of the actin-Tm-myosin complex, we suppose that the physiological effects of these mutations in Tm can be accounted for by their influence on the interactions between the central part of Tm and certain sites of the myosin head.
