The main constituent of the thick filaments is myosin. Each thick filament is composed of about 250 molecules of myosin. Myosin has two important roles: a structural one, as the building block for the thick filaments, and a functional one, as the catalyst of…

What are the two sites on a myosin head?

The globular myosin heads extend outward and form cross-bridges when they interact with thin filaments. The myosin heads have two reactive sites: One allows it to bind with the actin filament, and one binds to ATP.

Where are the myosin molecules located?

Where Is Myosin Found? In both eukaryotic cells, cells that have membrane-bound organelles and a nucleus, and prokaryotic cells, cells that lack a nucleus and membrane-bound organelles, we can find myosin. It exists as a filament inside of the cell.