Keratin is a protein inside cells. It occurs in many types of cells but is very important for epithelial cells that form the skin. Keratin is a type of filamentous protein, called indirect filament. These proteins form long strands inside the cell, hence the name of the fiber. The fibers anchor the cells to each other, which prevents the cells from detaching.
Keratin has two main functions in the skin:
1. To keep skin cells together, creating a barrier
2. To create the outermost layer of our skin that protects us from the environment.
To create a barrier, epithelial cells anchor together through proteins called desmosomes. Two epithelial cells stand next to each other and connect using desmosomes. Desmosomes are like glue holding two cells together. Inside the cell, there are keratin fibers that support desmosomes in the cell. Without keratin fibers, desmosomes will simply pull the cell membrane from the inside. Keratin anchors desmosomes to the cell, and desmosomes anchor cells to each other. See the desmosome connector? The cells combine with each other, and long fibers in combination are keratin proteins.
For example, murine thymic epithelial cells (TEC) are known to react with antibodies to keratin 5, keratin 8 and keratin 14. These antibodies are used as fluorescent markers to distinguish between TEC subsets in thymic genetic studies.
α-keratin is present in all vertebrates. They form hair (including wool), stratum corneum, horns, nails, claws and hooves of mammals and mucous membranes.
harder β-keratin are found only in the European region, that is, in all live reptiles and birds. They find in nails, scales, and claws of reptiles, some reptile shells (Testudines, such as turtle, tortoise, terrapin) and in bird feathers, beaks and claws. However, beta-keratin also have beta sheets.)
In addition, whalebone whale feeding panels are made of keratin.
Keratin is polymers of type I and type II intermediate fibers that have only been found in the genomes of chords (vertebrates, Amphioxus, urochordates). Nematodes and many other animals without chords seem to have only indirect type VI, lamina fibers, which have a long rod domain (compared to the short domain of rods for keratin).