What is the regulatory protein component of the thin filament that binds to calcium

Troponin

Explanation:

Myofilaments are found in myofibrils and comprises of thin and thick filaments. Thick filaments are majorly composed of myosin while thin filaments are mainly composed of actin protein.

More specifically thin filament is composed of three proteins known as actin, myosin and troponin. Sarcomere is known as the basic contractile unit and in vertebrates the contraction of striated muscles is mainly controlled by interaction of troponin and tropomyosin on actin filament.

On the stimulation from the nervous system the calcium ions are released from sarcoplasmic reticulum. The tropomyosin filament is moved on actin filament to uncover the surface for the binding of myosin head by the stimulation from calcium ion binding to troponin. This causes the contraction of sarcomere and it continues until the calcium ions are removed from sarcoplasmic reticulum.