Keratin

Keratin (/ˈkɛrətɪn/) is one of a family of fibrous structural proteins. Keratin is the protein that protects epithelial cells from damage or stress that has potential to kill the cell. It is the key structural material making up the outer layer of human skin. It is the key structural component of hair and nails, and it provides the necessary strength and toughness for masticatory organs, such as the tongue and the hard palate. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and form strong unmineralized tissues found in reptiles, birds, amphibians, and mammals. The only other biological matter known to approximate the toughness of keratinized tissue is chitin.

Etymology

Keratin derives from Greek κερατίνη from Greek keras (κέρας) (genitive keratos, κέρατος) meaning "horn" originating from the Proto-Indo-European *ḱer- of the same meaning. It is composed of "horn like", i.e., kerato, to which the chemical suffix -in is appended.

Examples of uses

Keratin 12

Keratin 12 is a protein that in humans is encoded by the KRT12 gene.

Keratin 12 is keratin found expressed in corneal epithelia. Mutations in the gene encoding this protein lead to Meesmann corneal dystrophy.

References

Further reading

Keratin 6A

Keratin 6A is one of the 27 different type II keratins expressed in humans. Keratin 6A was the first type II keratin sequence determined. Analysis of the sequence of this keratin together with that of the first type I keratin led to the discovery of the four helical domains in the central rod of keratins. In humans Keratin 6A is encoded by the KRT6A gene.

Keratins

Keratins are the intermediate filament proteins that form a dense meshwork of filaments throughout the cytoplasm of epithelial cells. Keratins form heteropolymers consisting of a type I and a type II keratin. Keratins are generally expressed in particular pairs of type I and type II keratin proteins in a tissue-specific and cellular differentiation-specific manner.

The keratin proteins of epithelial tissues are commonly known as "keratins" or are sometimes referred to as "epithelial keratins" or "cytokeratins". The specialized keratins of hair and nail are known as "hard keratins" or "trichocyte keratins". Trichocytes are the specialized epithelial cells from which hair and nail are composed. Trichocyte keratins are similar in their gene and protein structure to keratins except that they are especially rich in the sulfur-containing amino acid cysteine, which facilitates chemical cross-linking of the assembled hard keratins to form a more structurally resilient material.