Final answer:
Thick filaments are primarily composed of myosin, which connects at the M line and has heads that interact with thin filaments made of actin. Nebulin also plays a role in the structure of thick filaments.
Step-by-step explanation:
The proteins that make up a thick filament are myosin and nebulin . Myosin molecules connect to each other by their tails to form the central region of the thick filament near the M line, with the heads of the myosin molecules extending outwards where they can interact with thin filaments. Nebulin is an actin-binding protein that plays a role in maintaining the alignment and length of the actin thin filament.
The main component of thin filaments is actin, which works together with myosin to enable muscle contractions. Thick filaments in muscle cells are composed of the protein myosin. The tail of a myosin molecule connects with other myosin molecules to form the central region of a thick filament near the M line, whereas the heads align on either side of the thick filament where the thin filaments overlap.