When Tropomyosin Changes Shape What Happens?

To enable a muscle contraction, tropomyosin must change conformation, uncovering the myosin-binding site on an actin molecule and allowing cross-bridge formation. This can only happen in the presence of calcium, which is kept at extremely low concentrations in the sarcoplasm.

What causes troponin to change shape?

When calcium binds to troponin, the troponin changes shape, removing tropomyosin from the binding sites. The sarcoplasmic reticulum stores calcium ions, which it releases when a muscle cell is stimulated; the calcium ions then enable the cross-bridge muscle contraction cycle.

What is the shape of tropomyosin?

Tropomyosin is a two-stranded alpha-helical, coiled coil protein found in actin-based cytoskeletons.