Final answer:
Tropomyosin is a protein that prevents muscle contraction by covering myosin-binding sites on actin filaments. It works with troponin to regulate the interaction between actin and myosin, and is displaced when calcium ions bind to troponin during muscle activation.
Step-by-step explanation:
Tropomyosin is a fibrous protein that plays a crucial role in muscle contraction by winding around the actin filaments. This protein works alongside troponin to regulate the interaction between actin and myosin through its position along the actin filament. When a muscle is at rest, tropomyosin covers the myosin-binding sites on the actin chains, preventing muscle contraction. However, when the muscle receives a signal to contract, calcium ions (Ca++) bind to troponin, causing a conformational change that moves tropomyosin away from the binding sites, allowing myosin heads to attach to actin and facilitate muscle contraction.