Fig. 2.

Schematic drawing to scale of essential components of the sarcomere. Tropomyosin (Tm) and the three subunits of troponin (Tn complex) decorate the actin filament. The domains of myosin are the S1 head (only one of two are shown for clarity), the coiled-coil S2, and the light meromyosin that forms the thick filament (bottom grey platform). The N-terminal domains of myosin binding protein-C (MyBP-C) bind to the thin actin filament and the C-terminal domains bind to the thick myosin filament. Titin (not shown) traverses in between the thin and thick filaments, closely associated with the thick filament backbone. Interactions among titin, MyBP-C, S1, and S2 are possible and perhaps regulatory, but have not been fully explored.