Troponin C

Troponin C (TnC) is a part of the troponin complex, a group of three regulatory proteins (troponin C, troponin I, and troponin T) that are integral to muscle contraction in skeletal and cardiac muscle. Troponin C is the calcium binding component of the complex.

Structure

Troponin C is a small protein of about 18 kDa that binds calcium ions to regulate muscle contraction. It is composed of two domains, each of which can bind two calcium ions. The N-terminal domain is the regulatory domain and binds calcium ions in a cooperative manner, while the C-terminal domain binds calcium ions non-cooperatively.

Function

The primary function of troponin C in the troponin complex is to bind calcium ions and initiate muscle contraction. When calcium ions bind to troponin C, a conformational change occurs in the troponin complex that allows tropomyosin to move and expose the myosin-binding sites on actin filaments. This enables the myosin heads to bind to actin and initiate muscle contraction.

Clinical significance

Alterations in the structure or function of troponin C can lead to various muscle disorders. Mutations in the TNNC1 gene, which encodes for troponin C, have been associated with idiopathic dilated cardiomyopathy, a condition characterized by weakening of the heart muscle. Additionally, elevated levels of troponin C in the blood can be an indicator of heart damage, such as that which occurs during a myocardial infarction.

See also

• Troponin I
• Troponin T
• Tropomyosin
• Actin
• Myosin
• Cardiomyopathy
• Myocardial infarction