What is the primary role of the muscle protein Titin?

The primary role of the muscle protein Titin is to provide structure and elasticity to the sarcomere. Titin is one of the largest known proteins and plays a crucial role in maintaining the integrity and function of the sarcomere, which is the basic unit of muscle contraction. It spans half of the sarcomere, anchoring myosin filaments to the Z-disc and helping to align the thick and thin filaments during muscle contraction and relaxation.

By providing structural support, Titin prevents overextension of the sarcomere and contributes to passive stiffness, which is essential for the muscle's ability to return to its original shape after being stretched. This elasticity is important for storing elastic energy and contributes to the overall efficiency of muscle contractions. Thus, Titin plays a fundamental role in muscle mechanics, ensuring proper function during the contraction cycle by maintaining the organization of the sarcomere and contributing to the elastic properties of muscle tissue.