Question

Actin binding sites are located on

(i) Myosin

(ii) Tropomyosin

(iii) Troponin

• A. (i)
• B. (i) and (ii)
• C. (i) and (iii)
• D. (i), (ii) and (iii)

Answer 1

The correct option is D

(i), (ii) and (iii)

Both troponin and tropomyosin bind to actin in the resting state of the muscle and prevent the binding of myosin. In the presence of $C{a}^{2+}$ ions, the myosin-binding sites of actin are uncovered. The myosin can then bind to actin and initiate contraction.