Understanding Actin Filament Sliding: Preventing Backward Movement

When a myosin head releases after the power stroke, the binding of ADP to the myosin head decreases its affinity for the actin-binding site. However, detachment of the myosin head is prevented because another myosin head binds to the thin filament before the first one can completely detach. This is termed the "hand-over-hand" mechanism.

Additionally, tropomyosin, a regulatory protein located on the thin filament, prevents the backward sliding of actin myofilaments in the absence of calcium ions. When calcium ions bind to troponin, conformational changes occur in the complex, allowing myosin heads to interact with the actin-binding sites.