Aberrant movement of β-tropomyosin associated with congenital myopathy causes defective response of myosin heads and actin during the ATPase cycle

[Display omitted] •Polarized fluorimetry was used to determine the position of β-TM in troponin-free ghost fibers during the ATPase cycle.•Each state corresponds to a certain combination of several positions of the wild-type β-TM.•The counter motion of the wild-type β-TM and actin during the ATPase cycle is observed.•The E41K, R91G and E139del mutations in β-TM induce its abnormal movement during the ATPase cycle.•Response of actin monomers and myosin heads to the movement of the mutant TMs is defective. We have investigated the effect of the E41K, R91G, and E139del β-tropomyosin (TM) mutations that cause congenital myopathy on the position of TM and orientation of actin monomers and myosin heads at different mimicked stages of the ATPase cycle in troponin-free ghost muscle fibers by polarized fluorimetry. A multi-step shifting of wild-type TM to the filament center accompanied by an increase in the amount of switched on actin monomers and the strongly bound myosin heads was observed during the ATPase cycle. The R91G mutation shifts TM further towards the inner and outer domains of actin at the strong- and weak-binding stages, respectively. The E139del mutation retains TM near the inner domains, while the E41K mutation captures it near the outer domains. The E41K and R91G mutations can induce the strong binding of myosin heads to actin, when TM is located near the outer domains. The E139del mutation inhibits the amount of strongly bound myosin heads throughout the ATPase cycle.