ANATOMY

Detailed explanation-1: -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.

Detailed explanation-2: -Troponin C (TnC; 18 kDa) is the calcium-binding component of the contractile apparatus and upon binding intracellular Ca2 + ions induces a conformational change in the troponin–tropomyosin complex, reducing TnI inhibition of the actinomysin ATPase and allowing muscle contraction to occur [18].

Detailed explanation-3: -The calcium ions released from endoplasmic reticulum72) bind to the calcium-binding subunit of troponin (troponin-C (TnC), ∼18 kDa), and the inhibition by troponin is neutralized to trigger muscle contraction.

Detailed explanation-4: -Troponin binds to tropomyosin and helps to position it on the actin molecule; it also binds calcium ions.

Detailed explanation-5: -An increase in free calcium concentration results in a conformational change within the troponin complex that releases tropomyosin into a “closed” position that allows weak actin-myosin interaction7. Strong binding of myosin to actin further shifts tropomyosin to the “open” position.