Figure 1.

Structure of a homology-modeled human β-cardiac sS1 domain showing the positions of two mutations that cause early onset HCM. (a) Structure of homology-modeled human β-cardiac sS1, containing residues 1-808 of the MHC (grey) and the ELC (brown). The positions of the HCM mutations H251N (blue) and D239N (red) are shown. (b) Sphere model of sS1 shown in (a) rotated ~90° about the horizontal axis toward the reader, viewing the mesa from the top. The position of the mutation H251N on the mesa is seen in the middle of a cluster of other positively charged residues, all of which cause HCM when mutated (Spudich, 2015).