Thin filament flexibility and its role in muscle contraction

Contemporary experimental methods do not allow unequivocal determination of molecular structural events during muscle contraction. To analyze existing contradictions, an original computer program has been developed. This program reconstructs the hexagonal lattice of a sarcomere for different states of muscle and finds the most realistic structure by comparing the calculated Fourier spectrum with the actual diffraction pattern. Previously, the new approach allowed reconstructing the actual structure of a myosin filament from mammalian striated muscle (http://zope.ibib.waw.pl/pspk). In this work, the thin filament is reconstructed for three states: relaxed, activated, and contracting. The good fit between the calculated Fourier spectra and the actual diffraction patterns taken from the literature suggests that the thin filament owing to its flexibility may play an active role in muscle contraction, as myosin cross-bridges do.