MUSCLE PHYSIOLOGY

Detailed explanation-1: -Specifically, troponin (the smaller protein) shifts the position of tropomyosin and moves it away from the myosin-binding sites on actin, effectively unblocking the binding site (Figure 5). Once the myosin-binding sites are exposed, and if sufficient ATP is present, myosin binds to actin to begin cross-bridge cycling.

Detailed explanation-2: -Regulation of Troponin and Tropomyosin If present, calcium ions bind to troponin, causing conformational changes in troponin that allow tropomyosin to move away from the myosin-binding sites on actin. Once the tropomyosin is removed, a cross-bridge can form between actin and myosin, triggering contraction.

Detailed explanation-3: -Once bound, tropomyosin polymerizes end-to-end and both stabilizes F-actin and regulates access of various actin binding proteins including myosin in muscle and non-muscle cells.

Detailed explanation-4: -At low Ca2+ concentration, troponin constrains tropomyosin in a “blocking-position” over the myosin-binding sites on actin, thereby inhibiting the acto/myosin-crossbridge cycle and consequently relaxing muscles.