Figure 1.

Overview of the sarcomeric structure and the contractile acto-myosin apparatus of skeletal muscle. The diagram to the left outlines the arrangements of the thick myosin-containing filament, the half-sarcomere spanning titin filament and the actin/nebulin-containing thin filament in relation to their positions within the A-band, the I-band, the H-zone, the M-line and the Z-disc structures of the sarcomere. The diagram to the right shows the interactions between the head structure of myosins and filamentous actin molecules that are involved in the crossbridge formation during skeletal muscle contractions. Details of the subunit composition and isoform diversity of myosin heavy chains, myosin light chains, myosin binding proteins, actins, tropomyosins and troponins are given in Figure 2 below. Abbreviations used: ACT, actin; MLC, myosin light chain; MYBP, myosin binding protein; MyHC, myosin heavy chain; TNC; troponin-C; TNI; troponin-I; TNT, troponin-T; TPM, tropomyosin.