troponin function in skeletal muscle
Dear student,
Troponins are arranged in a heterotrimeric complex consisting of 3 troponin molecules, whose names are derived from their functions: calcium-binding troponin C (Tnc), inhibitory troponin I (Tnl), and tropoImyosin-binding troponin T (TnT). The complex attaches to the thin filaments of muscle and acts to regulate late muscle contraction. The troponin isoforms expressed in muscle tissues differ based on the tissue's role, with cardiac myocyte uniquely expressing the cardiac Tnl (CTnl) and cardiac troponin T (cTnT) isoforms. This tissue specificity has driven the use of cardiac troponins as biomarkers for cardiac injury. Although there is a so-called cardiac troponin C (cTnC), it is expressed in both cardiac and slow skeletal muscle.
The troponin complex plays an essential role in regulating the excitation - contraction coupling in skeletal and cardiac muscle through calcium signaling. Without calcium bound by trponin C, the Tnl protein binds the heterotrimer to the thin filament. The binding of calcium by TnC causes a conformational change, exposing a hydrophobic section to which TnI preferentially binds. In doing so, the complex is able to swing away from the thin filament, allowing TnT to bind tropomyosin, and exposing actin binding sites that previously were covered by Tnl. This process drives muscle contraction.
Regards
Troponins are arranged in a heterotrimeric complex consisting of 3 troponin molecules, whose names are derived from their functions: calcium-binding troponin C (Tnc), inhibitory troponin I (Tnl), and tropoImyosin-binding troponin T (TnT). The complex attaches to the thin filaments of muscle and acts to regulate late muscle contraction. The troponin isoforms expressed in muscle tissues differ based on the tissue's role, with cardiac myocyte uniquely expressing the cardiac Tnl (CTnl) and cardiac troponin T (cTnT) isoforms. This tissue specificity has driven the use of cardiac troponins as biomarkers for cardiac injury. Although there is a so-called cardiac troponin C (cTnC), it is expressed in both cardiac and slow skeletal muscle.
The troponin complex plays an essential role in regulating the excitation - contraction coupling in skeletal and cardiac muscle through calcium signaling. Without calcium bound by trponin C, the Tnl protein binds the heterotrimer to the thin filament. The binding of calcium by TnC causes a conformational change, exposing a hydrophobic section to which TnI preferentially binds. In doing so, the complex is able to swing away from the thin filament, allowing TnT to bind tropomyosin, and exposing actin binding sites that previously were covered by Tnl. This process drives muscle contraction.
Regards