Figure 29-3 Ryanodine receptor 1 gene (RYR1) structure and mutational hot spots. Amino- and carboxyl-terminal domains are indicated as NH₂ and COOH, respectively. Myoplasmic and transmembrane domains are shown at the bottom and arrows indicate dihydropyridine receptor (DHPR) and calmodulin binding sites. Red boxes indicate mutational hot spots with amino acid numbers below. The ovals above represent mutations associated with malignant hyperthermia (gray), central core disease (black), or both (red). (Courtesy of N. Sambuughin, Barrow Neurological Institute, Phoenix, AZ.)