In skeletal muscles, which protein does Ca2+ bind to for tropomyosin removal?

In skeletal muscle, the binding of calcium ions (Ca2+) is crucial for initiating muscle contraction. When calcium is released into the cytoplasm of a muscle cell, it binds specifically to the troponin complex, which is a protein that plays a key role in the regulation of muscle contraction.

The troponin complex consists of three subunits: troponin C (the one that binds calcium), troponin I (which inhibits actin-myosin interaction), and troponin T (which binds to tropomyosin). When Ca2+ attaches to troponin C, it causes a conformational change in the troponin complex. This change results in the movement of tropomyosin away from the binding sites on actin filaments. Once tropomyosin is displaced, the myosin heads can bind to actin, leading to muscle contraction.

Thus, the interaction between calcium and troponin is critical for the regulation of contraction in skeletal muscles, effectively removing the inhibitory effect of tropomyosin and allowing for cross-bridge formation between actin and myosin.