Question

What three polypeptides comprise the globular polypeptide complex structure of troponin, and what are their respective functions?

a) Tropomyosin - blocks myosin binding, Troponin I - inhibits actin-myosin interaction, Troponin T - binds troponin to tropomyosin
b) Troponin I - inhibits actin-myosin interaction, Troponin T - binds troponin to tropomyosin, Troponin C - binds calcium
c) Troponin C - blocks myosin binding, Troponin T - inhibits actin-myosin interaction, Troponin I - binds troponin to tropomyosin
d) Tropomyosin - binds calcium, Troponin I - blocks myosin binding, Troponin C - inhibits actin-myosin interaction

Answer 1

The troponin complex is made up of troponin C which binds calcium, troponin I that inhibits actin-myosin interaction, and troponin T that anchors the complex to tropomyosin. They collectively regulate muscle contraction.

Step-by-step explanation:

The troponin complex, which is critical for muscle contraction, is composed of three distinct polypeptides: troponin C (TnC), troponin I (TnI), and troponin T (TnT). Each of these polypeptides plays a specific role in the regulation of muscle contraction.

• Troponin C (TnC) binds calcium ions, which is essential for initiating the muscle contraction process. When Ca++ ions bind to TnC, it triggers a conformational change in the troponin complex.
• Troponin I (TnI) inhibits actin-myosin interaction by stabilizing the position of tropomyosin over the actin filament, thereby preventing the myosin heads from binding to actin in the absence of calcium.
• Troponin T (TnT) binds to tropomyosin, anchoring the troponin complex to the actin filament.

Montaltogether, this troponin-tropomyosin complex ensures that the muscle remains relaxed until the presence of Ca++ ions, after which the structure of troponin changes to allow muscle contraction to occur.