Troponin I (104-115) is a cardiac and skeletal muscle protein useful in the laboratory diagnosis of heart attack. It occurs in different plasma concentration but the same circumstances as troponin T - either test can be performed for confirmation of cardiac muscle damage and laboratories usually offer one test or the other._x000D_
Troponin I is a part of the troponin protein complex, where it binds to actin in thin myofilaments to hold the actin-tropomyosin complex in place. Because of it, myosin cannot bind actin in relaxed muscle. When calcium binds to the troponin C it causes conformational changes which lead to dislocation of troponin I and finally tropomyosin leaves the binding site for myosin on actin leading to contraction of muscle. The letter I is given due to its inhibitory character.
