Fig. 1: Structure of the primed actomyosin-5 complex.

a,b, Cryo-EM density map of the primed actomyosin-5 complex, segmented and coloured by myosin subdomains and actin chains as indicated (with the central three actin subunits displayed). Actin subunits are shown in slate grey (−actin, nearer the filament pointed (−) end), blue-grey (+actin, nearer the barbed (+) end) and light grey; the nucleotide is shown in sky blue. The map is thresholded to show secondary structure (myosin 0.085, actin 0.2) and is shown in side view of F-actin (a) and in end-on view of F-actin, looking towards the pointed end (b). c, Backbone depiction of a pseudo-atomic model of primed actomyosin-5, fitted into the EM density map, viewed as in b. d, Magnified side view of the actomyosin interface; the main contacts are made by the myosin HLH motif and loop 3, as observed in strongly bound states. e, Additional contacts are made by loop 2 (EM density threshold 0.007). Relevant interacting residues are labelled and shown. f, The lever helix points along the actin axis towards the pointed end, at an angle of about 52° to the actin axis. g, Magnified view showing the N-terminal residues (D1 and E2) of the −actin subunit (slate grey), interacting with helix W (H637 and N641) of the L50 domain, and loop 2 (H631) (EM density threshold 0.007). A DeepEMhancer post-processed map is depicted in a–d,f, and a RELION post-processed map is depicted in e,g.