Actin

Actin is a protein macromolecule that is one of the basic components of the actin myofilament – ​​a complex structure that forms the contractile apparatus of the muscle fiber (in addition to actin, troponin and tropomyosin - they are also part of the actin myofilament).

Structure
The skeleton of the actin myofilament is formed by F-aktin in the form of a 1 μm long double helix. This double helix is ​​made up of more than 400 G-aktin. Each of the G-actin molecules contains a place that is capable of interacting with the „head“ of myosin. This place is blocked by the tropomyosin molecule during the state of relaxation of the contractile complex.

For more detailed information, see Excitation-contraction coupling in skeletal muscle.



Related articles

 * Myosin
 * Myofibril ultrastructure, contraction mechanism
 * Muscle
 * Connection of excitation and contraction