Which of the following is not the component of cross arm?

The calcium binding site is on the troponin-C subunit of the thin filament. When calcium binds to troponin, it triggers the movement of tropomyosin, exposing the binding sites on actin for myosin.

Myosin of the thick filament has binding sites for actin and ATP. The head of myosin acts as ATPase, facilitating the hydrolysis of ATP to provide energy for muscle contraction.

The thick filament is composed of both heavy meromyosin (HMM) and light meromyosin (LMM).