The troponin complex controls muscle contraction by moving tropomyosin, a protein that blocks myosin from binding to actin when the muscle is relaxed. It consists of three subunits: Troponin C (TnC), Troponin I (TnI), and Troponin T (TnT). Troponin C (TnC) detects calcium. When a muscle fiber receives an electrical signal, calcium ions (Ca²⁺) are released from the sarcoplasmic reticulum into the sarcoplasm. These ions bind to TnC, causing it to change shape. TnC has two binding sites that always