Contractile Protein with ATPase Activity in Skeletal Muscle

Contractile protein of skeletal muscle involved in ATPase activity is:

Correct Answer: Myosin

The myosin head (S1 subfragment) has intrinsic ATPase activity. It hydrolyzes ATP to ADP + Pi, releasing energy that drives the power stroke of muscle contraction.

Why Myosin Has ATPase Activity

• The myosin head binds to actin and uses ATP energy to pivot (power stroke), pulling the thin actin filament toward the M-line.
• ATPase activity: Myosin-ATPase cleaves ATP → ADP + Pi → energy released → cross-bridge cycling → muscle shortening.

Actin vs. Myosin

• Actin: Thin filament; does NOT have ATPase activity; it is the 'track' on which myosin walks.
• Myosin: Thick filament; the 'motor protein'; has ATPase activity in the head region.
• Troponin: Regulatory protein complex (C, T, I subunits); no ATPase activity.
• Tropomyosin: Regulatory protein; blocks actin's binding sites for myosin at rest.