Looking for Targets to Restore the Contractile Function in Congenital Myopathy Caused by Gln147Pro Tropomyosin

Figures

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  Figure 1. A typical pattern of changes in the angle of orientation of emission dipoles ΦE for fluorescent probes associated with actin (Actin-FITC, or Actin*, a), tropomyosin (Tpm-AF, or Tpm*, b) and in the values of ΦE and the relative number of disordered fluorophores N for probe bound to S1 (S1-AEADANS, S1*, c,d) in ghost fibers containing reconstituted thin filaments with control recombinant Tpm (of wild type, WT) and troponin (TN). The values are compared at high (orange columns) and low (green columns) Ca2+ concentrations. Black color is used for the values obtained in ghost fibers not containing troponin.

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  Figure 2. The changes in the value of ε—bending stiffness—for the fluorescent probes bound to actin (Actin-FITC, or Actin*, a) and Tpm (Tpm-AF, or Tpm*, b) in ghost fibers containing recombinant WT and Q147P-mutant Tpms in the absence of troponin (black and red columns) and in the presence of troponin at low and high Ca2+-concentrations (see legend). The increase in the value of ε means the increase in the persistence lengths of actin and Tpm filaments.

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  Figure 3. The effect of the Q147P substitution in Tpm on the angles of orientation of emission dipoles ΦE for fluorescent probes associated with actin (Actin-FITC, or Actin*, a), tropomyosin (Tpm-AF, or Tpm*, b) and on the values of ΦE and relative number of disordered fluorophores N for fluorescent probe associated with S1 (S1-AEADANS, or S1*, c,d) in ghost fibers containing reconstituted thin filaments with mutant recombinant Tpm and troponin (TN) at high (dark red columns) and low (yellow columns) Ca2+ concentrations. The changes in the values are given relative to the WT Tpm (see Figure 1) in the same order and are significantly different (p < 0.05) except the values indicated as nonsignificant—ns. Red color is used for the values obtained in ghost fibers not containing troponin. An increase in the value of ΦE for actin-FITC occurs at switching actin on, while a decrease in the values of ΦE for Tpm-AF and S1-AEDANS is typical for the shift of Tpm towards the open position in actin groove and for increase in the number of the myosin heads in the strong-binding state.

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  Figure 4. The schematic view of the changes in the conformational rearrangements of actin monomers and the myosin heads and in the position of Tpm caused by the congenital-myopathy-causing mutation Q147P in Tpm2.2. The muscle fibers contained Tpm and troponin at a low Ca2+ concentration (simulated blocked state), at a high Ca2+ concentration (closed state) or Tpm, troponin and S1 in the absence of nucleotide (M state) and in the presence of ATP (MATP state). Several proposed positions of Tpms related to the values of ΦE are shown on top. The numbers close to Tpm, actin, and the myosin head are used to designate the changes under the substitution in the values of ΦE for actin-FITC, Tpm-AF and S1-AEDANS as compared with the respective changes in the presence of WT Tpm.