Troponin and tropomyosin are regulatory proteins that help to regulate the interaction between actin and myosin filaments. 

The binding of the myosin heads to the muscle actin is a highly regulated process. When a muscle is resting, actin and myosin are separated. To keep actin from binding to the active site on myosin, regulatory proteins block the molecular binding sites. These regulatory proteins are tropomyosin and troponin. Tropomyosin covers the actin-binding sites, preventing myosin from forming cross-bridges while in a resting state. Troponin binds to tropomyosin and helps to position it on the actin molecule. 

Key Points

• Troponin and tropomyosin are regulatory proteins that block the interaction between the actin and myosin while the muscle rests.

• Tropomyosin covers the actin-binding sites, preventing myosin from forming cross-bridges while in a resting state; troponin binds to tropomyosin and helps to position it on the actin molecule.

Key Terms

Actin: A protein which interacts with myosin filaments to generate tension.

Myosin: A motor protein which interacts with actin filaments to generate tension.

Tropomyosin: an actin-binding protein that regulates muscle contraction

Troponin: a complex of three proteins, attached to tropomyosin