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Actin is a family of globular multi-functional proteins that form microfilaments in the cytoskeleton, and the thin filaments in muscle fibrils.It is found in essentially all eukaryotic cells, where it may be present at a concentration of over 100 μM; its mass is roughly 42 kDa, with a diameter of 4 to 7 nm.
The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. [2] In eukaryotes , it extends from the cell nucleus to the cell membrane and is composed of similar proteins in the various organisms.
Initially, a 55 kDa protein was isolated from the actomyosin complex of Dictyostelium discoideum, which was later shown to bind actin in vitro. [4] This actin binding protein was named coronin after its strong immunolocalisation in the actin rich crown like extension of the cell cortex in D. discoideum.
Profilin is an actin-binding protein involved in the dynamic turnover and reconstruction of the actin cytoskeleton. [1] It is found in most eukaryotic organisms. Profilin is important for spatially and temporally controlled growth of actin microfilaments, which is an essential process in cellular locomotion and cell shape changes.
[1] [2] [3] In most eukaryotic cells lacking a cell wall, the cortex is an actin-rich network consisting of F-actin filaments, myosin motors, and actin-binding proteins. [ 4 ] [ 5 ] The actomyosin cortex is attached to the cell membrane via membrane-anchoring proteins called ERM proteins that plays a central role in cell shape control.
Microfilaments, also called actin filaments, are protein filaments in the cytoplasm of eukaryotic cells that form part of the cytoskeleton. They are primarily composed of polymers of actin , but are modified by and interact with numerous other proteins in the cell.
Compared to the other parts of the cytoskeletons, the microfilaments contain the thinnest filaments, with a diameter of approximately 7 nm. Microfilaments are part of the cytoskeleton that are composed of protein called actin. Two strands of actin intertwined together form a filamentous structure allowing for the movement of motor proteins.
All organisms contain organelles that provide physical integrity to their cells. These type of organelles are collectively known as the cytoskeleton, and one of the most ancient systems is based on filamentous polymers of the protein actin. A polymer of a second protein, tropomyosin, is an integral part of most actin filaments in animals.