Write short notes on contractile proteins.

Thin filament : It is made of 3 kinds of proteins
* Actin : It is in the form of two filamentous molecule. Each F-actin made up of G-actin molecules.
* Troponin : It is made up of 3 polypeptide units namely Tn–I, Tn–c, and Tn–T. Tn–T binds to
Tropomyosin.
* Tropomyosin : It runs close to 'F' actin molecules all along the length of actin.
Thick filaments :
* Myosin : It is made up of several monomeric proteins called meromyosin.
* Each meromyosin has a globular head, short neck and tail.
* Head has two binding sites one for ATP and other for active site. (Actin binding site)