The dystrophin molecule and its partners. (A) Schematic representation of the molecule with the structural domains CH1 and CH2, constituting actin-binding domain 1, hinges 1 to 4 (H1 to H4), spectrin-like repeats 1 to 24 (R1 to R24); the WW domain and EF hand–region constituting the Cys-rich domain; ZZ, the zinc finger domain; and the C-terminal domain (C term) and its partners. (B) Model of the three-dimensional structure of repeat 7 folded into a triple coiled-coil, consisting of three helices, A, B, and C, joined by two loops, AB and BC. (C) Model of the three-dimensional structure of tandem repeats R7-8 of the rod domain. Each repeat is composed of three alpha helices folded into a triple coiled-coil: R7 (helices A, B, and C, joined by loops AB and BC) and R8 (helices A’, B’ and helix C’, joined by loops A’B’ and B’C’). A long common helical linker is formed between the two repeats by R7 helix C and R8 helix A’.