Thin Filaments (Actin, Troponin, Tropomyosin)

Troponin

Aids in exposure of the binding sites.

Actin

Arranged in 2 single strands that intertwine helically and give them their shape.

Troponin

By itself, cannot move tropomyosin away from the binding site on actin. This process requires calcium ions. After an action potential, calcium ions are released from the terminal cisternae and bind to the ________. This causes a confromational change in the tropomyosin-troponin complex, "dragging" the tropmyosin strands off the binding sites.

Troponin

Calcium attaches here.

Tropomyosin

Entwines around the actin.

Tropomyosin

In the unstimulated muscle, the position of the tropomyosin covers the binding sites on the actin subunits and prevents myosin cross bridge binding.

Troponin

Located at regular intervals on the surface of tropomyosin.

Actin

Looks like a string of pearls, helically twisted.

Tropomyosin

Looks like a vine, covering the bonding site on actin.

Troponin

Looks like an up-side down snowman.

Actin

Protein subunit contains a myosin - binding site.

Actin

The major component of the thin filament.

Tropomyosin

The regulatory protein, tropomyosin is also part of the thin filament.

Tropomyosin

To expose the binding sites for binding with myosin, the ________ molecule must be moved aside.

Tropomyosin-Troponin Complex

Together, tropomyosin and troponin are referred to as the ________.