Keratin Keratin Keratin () is one of a family of fibrous structural proteins. It is the key structural material making up hair, horns, claws, hooves, and the outer layer of human skin. Keratin is also the protein that protects epithelial cells from damage or stress. Keratin is extremely insoluble in water and organic solvents. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and form strong unmineralized epidermal appendages found in reptiles, birds, amphibians, and mammals. The only other biological matter known to approximate the toughness of keratinized tissue is chitin. Keratin derives from Greek ' from '
Keratin about 10 µm across, with cores and coating, and may be arranged in up to 10 layers, also in plaques of variable shape. Adult hornets also use silk as a glue, as do spiders. Some infectious fungi, such as those that cause athlete's foot and ringworm (i.e. the dermatophytes), or "Batrachochytrium dendrobatidis" (Chytrid fungus), feed on keratin. Diseases caused by mutations in the keratin genes include: Keratin expression is helpful in determining epithelial origin in anaplastic cancers. Tumors that express keratin include carcinomas, thymomas, sarcomas and trophoblastic neoplasms. Furthermore, the precise expression pattern of keratin subtypes allows prediction of the