Question

List five proteins of the myofilaments and describe their physical arrangement

Answer 1

The five proteins of the myofilaments are the following:

1.  Myosin, shaped like a golf club, with two polypeptides intertwined to form a shaftlike tail and a double globular head, or cross-bridge, projecting from it at an angle.

2. Fibrous actin is like a bead necklace—a string of subunits called globular (G) actin. Each G actin has an active site that can bind to the head of a myosin molecule.

3. Tropomyosin. It blocks the active sites of six or seven G actins and prevents myosin cross-bridges from binding to them when a muscle fiber is relaxed.

4. Troponin a smaller calcium-binding protein bound to each tropomyosin molecule.

5. Titin (connectin), run through the core of a thick filament, emerge from the end of it, and connect it to a structure called the Z disc.