What is troponin?

Troponin is a regulatory protein found in the myocardium, which is the muscular tissue of the heart. It plays a critical role in the process of muscle contraction. Troponin is part of the troponin complex, which includes three subunits: troponin C, troponin I, and troponin T. These subunits interact with calcium ions, allowing for the regulation of muscle contraction in cardiac and skeletal muscle.

When calcium levels rise in the muscle cells during the excitation-contraction coupling process, troponin C binds to calcium, causing a conformational change that allows tropomyosin to move away from the binding sites on actin filaments. This process enables the interaction of actin with myosin, leading to muscle contraction.

The presence of troponin in the bloodstream is also clinically significant, as elevated troponin levels are associated with myocardial injury, making it an important biomarker for diagnosing conditions like myocardial infarction (heart attack). This unique function distinguishes troponin from other choices, establishing its essential role in cardiac physiology.