Question

Major protein in the thick filaments of skeletal muscle fibre is
(a) Myosin
(b) Actin
(c) Tropomyosin
(d) Troponin

Answer 1

Troponin and tropomyosin both protein helps in muscle contraction. The actin filament is also known as Thin filament and the myosin filament is also known as thick filament and the tropomyosin covers the binding site for myosin on actin.

Complete answer:
The myosin filament is also known as the thick filament of size 100Å. The myosin filament is made up of several monomeric proteins known as meromyosin. The myosin filament does not show sliding movement during muscle contraction because it has a rough surface due to cross bridges. It is found in the A-band of muscles.
The actin filament is also known as Thin filament and it is thinner than myosin filament of size 50Å. It is maximum and shorter than myosin filament and six of the actin filament surrounds each myosin filament. It slides during muscle contraction due to a smooth surface and lack of cross-bridges. It consists of three proteins like actin, tropomyosin and troponin.
The actin filament is made up of F-actins and each F-actin is made up of monomeric globular actin. Throughout the length of F-actins, two filaments of tropomyosin protein are present and troponin is composed of three globular peptides at regular interval on tropomyosin and in thick filament meromyosin, the monomer of myosin is composed of a globular head with a short arm and tail. The globular head works as an active ATPase enzyme and it helps in the binding of ATP.

So, the correct answer is 'Myosin'.

Note:
As myosin is the major muscle protein in mammals its genes are present approx 25-30 from class I to class XV. It was observed that during mutation myosin II is absent due to which resistance is generated during multicellular morphogenesis.