What kind of protein molecules are the thick myofilaments made of?

Protein is an important part of all cells and tissues in human body. All important components of an organism need protein's participation. Generally speaking, protein accounts for about 18% of the total body mass, and the most important thing is related to life phenomena. Protein is the material basis of life and an organic macromolecule.

Coarse myofilament is one of the components of myofibrils in striated muscle cells, which is mainly composed of myosin. Myosin is long rod-shaped, and one end expands into a ball. There are about 200-300 myosins in a thick myofilament, which are arranged in parallel and staggered to form the trunk of the thick myofilament. The spherical head of each molecule is distributed at both ends of the trunk of the thick myofilament according to a specific arrangement.

Coarse muscle filaments and filaments.

Muscle fibers contain many myofibrils, which are cylinders composed of muscle protein. These protein can make muscle cells contract. Myofibrils contain two kinds of myofilaments parallel to the long axis of fibers. These myofilaments are arranged in a hexagonal shape and are divided into thick myofilaments and thin filament. There are six filaments around each thick muscle filament.

Both the thick myofilament and thin filament are attached to another structure called Z-disk or Z-line, which is perpendicular to the long axis of the fiber (myofibrils from one Z-line to another Z-line are called sarcomere). Perpendicular to the Z line is a structure called transverse tubule or T-shaped tubule, which is actually a part of the cell membrane extending to the deep part of the fiber. Inside the fiber, along the long axis between T tubules is a membrane system called sarcoplasmic reticulum, which is used to store and release calcium ions that stimulate muscle contraction.

Coarse muscle filaments and filaments are responsible for the actual work of muscles, and their working methods are quite interesting. Coarse myofilaments consist of protein called myosin. At the molecular level, the thick myofilament is an axis composed of myosin molecules arranged in a cylinder. Filaments are made up of another kind of protein called actin, which looks like two strings of intertwined pearls.

During contraction, myosin thick myofilaments maintain actin filaments by forming transverse bridges. Thick muscle filaments pull filaments to shorten muscle segments. In muscle fibers, the signals indicating contraction are synchronized at the whole fiber level, so that all myofibrils constituting sarcomere are shortened at the same time.

There are two structures in the groove of each filament that can make the filament slide along the thick myofilament: a long rod-shaped protein called tropomyosin; A short globin complex called troponin. Tropomyosin and troponin are molecular switches that control the interaction between actin and myosin during contraction. During contraction, thin filament glides over the thick myofilament, shortening the sarcomere.