Schematic of the M-Band Network
(A) Principal sarcomere regions are marked by the letters Z, I, A, and M.
(B) Modular myomesin, titin, and obscurin/obscurin-like-1 proteins form an intricate M-band network with C-terminal myomesin dimers crosslinking myosin filaments. The inset highlights the interaction between myomesin and obscurin/obscurin-like-1, which has been mapped to linker sequence (L) located between the myomesin fibronectin (Fn-III) domains My4 and My5 and the third immunoglobulin (Ig) domain of obscurin/obscurin-like-1 (O3/OL3, respectively) (Fukuzawa et al., 2008).