Composite cryo-EM reconstructions of the human cardiac actin–β-myosin–tropomyosin complex. (A) Top: Composite cryo-EM map of the rigor actin–β-cardiac myosin II–tropomyosin complex. These reconstructions were created by combining the central portion of the actin-tropomyosin from the helical reconstructions and the S1 domain of myosin, including the essential light chain (ELC) from focused refinements. This figure was rendered in Chimerax using the surface zone tool (Pettersen et al., 2021). Bottom: Atomic model of the complex in the same orientation as the reconstruction above. (B). Top: Mg²⁺·ADP-bound complex composite map. The rendering of the ADP-bound complex was completed in the same fashion as the rigor complex. Bottom: Atomic model of the rigor complex in the same orientation as the reconstruction. The nucleotide is also indicated in both the reconstruction and model.