Which one of the following muscle protein plays an important role in contraction of both smooth and striated muscle?

Ans. D. Actina. In both smooth and striated muscle, contraction is produced by the cross- bridge cycle in which the cross-bridge on the thick filament binds to the actin molecule on the thin filament.b. In excitation-contraction coupling in striated muscle, calcium initiates contraction by binding to troponin.c. The calcium-activated troponin then acts to remove the tropomyosin-mediated inhibition of the actin-myosin interaction. In excitation-contraction coupling in smooth muscle, calcium initiates contraction by binding to calmodulin. The calcium-activated calmodulin then activates the myosin light chain protein kinase (MLCK) enzyme, which phosphorylates the myosin light chains. Actin-myosin interaction follows light-chain phosphorylation.