Tropomyosin movement from M-state positions during MD. To mimic the movement of tropomyosin following release of myosin from F-actin, MD simulations were initiated for atomic models of tropomyosin localized on F-actin as in reconstructions decorated with either WT-S1 or 7G-S1 (see Fig. 2, D and E), but here with no S1 present. The green reference line in the diagram shows the positions of tropomyosin at the beginning of MD (the 3–4 Å difference in two tropomyosin starting positions is not highlighted here). The blue and yellow bands show positions explored by tropomyosin cables during MD starting with those in respective wild-type and 7G-associated models. The orange line indicates the C-state position of tropomyosin (Yamada et al., 2020) approached by tropomyosin beginning from the wild-type position (blue band). Tropomyosin starting from the aberrant M-state induced by 7G-S1 rarely contacts the C-state position; on average it remains in place and in fact often moves towards the extreme inner domain of F-actin (yellow band), viz. in a path opposite to that normally expected.