Extended Data Fig. 2: Molecular dynamics analysis of actin N-terminal interactions with myosin loop2, helixW and the activation loop.

a,b, Portion of the primed actomyosin density map and fitted structures, displaying the putative interactions between -actin’s N-terminal region and myosin (a) helixW/loop2 and (b) activation loop. c–h, Time courses of the distance between atoms involved in interactions in primed actomyosin during three 100 ns molecular dynamics simulations (cyan, sea green, blue). Each interaction is identified at the top of its panel. ACE refers to the oxygen atom of the acetyl group of -actin D1. i,j, Same as a,b but showing the equivalent views for the postPS structure. k–p, Same as c–h but showing time courses of putative interactions in the postPS structure. For all time courses, the average % time that the interatomic distance is within bonding range (3.3 Å; horizontal dotted line in each time course) across the three replicates is shown in the top left of each plot, and within Extended Data Table 2. Note that the most significant change in distance between atoms involved in interactions is for E2(OE1)-N641(ND2) shown in panel e. This is because, within the simulations, E2 switched between interacting with N641(ND2) via its OE1 and its OE2 atom. N641 also switches side chain position to form metastable interactions with H637. Despite these alternative interactions, the interaction shown is populated the most (48 % of the time).