Write a note on the structure of contractille protein.

Explanation

1. Contraction of the muscle depends on the presence of contractile proteins such as actin and myosin.
2. The thick filament of muscle fibres are composed of the protein myosin. The thin filaments are formed of three types of proteins called actin, tropomyosin and troponin. These four proteins are know as contractile proteins.
Thick myofilament:
3. Each myosin filament is made up of a monomer called meromyosin which has two regions, a globular head, a short arm called heavy meromyosin (HMM) and a tail called light meromyosin (LMM).
The globular head is an ATPase enxyme which has binding sites for ATP and actin- binding site.
Thin myofilament:
4. It is composed of two interwined actin molecules. Actin has polypeptide subunits called G-actin (globular actin ) and F- actin (Filamentous actin).
F- actin is an polymer of monomeric G-Actin and also has a myosin- binding site.
5. The thin filaments also contain several regulatory proteins like tropomyosin and troponin which help in regulating muscles constraction.