Keratins

thumb|300px|Microscopy of keratin filaments inside cells

thumb|202px|right|Keratin intermediate filaments in epithelial cells (red stain). Cytokeratins are keratin proteins found in the intracytoplasmic cytoskeleton of epithelial tissue. They are an important component of intermediate filaments, which help cells resist mechanical stress. Expression of these cytokeratins within epithelial cells is largely specific to particular organs or tissues. Thus they are used clinically to identify the cell of origin of various human tumors.

Tonofibrils are cytoplasmic protein structures in epithelial tissues that converge at desmosomes and hemidesmosomes. They consist of bundles of keratin intermediate filaments (tonofilaments) in epithelial cells that are anchored to the cytoskeleton. They were discovered by Rudolf Heidenhain, and first described in detail by Louis-Antoine Ranvier in 1897.

protein-coding gene in the species Homo sapiens

Alpha-keratin, or α-keratin, is a type of keratin found in mammalian vertebrates. This protein is the primary component in hairs, horns, claws, nails and the epidermis layer of the skin. α-keratin is a fibrous structural protein, meaning it is made up of amino acids that form a repeating secondary structure. The secondary structure of α-keratin is very similar to that of a traditional protein α-helix and forms a coiled coil. Due to its tightly wound structure, it can function as one of the strongest biological materials and has various functions in mammals, from predatory claws to hair for war

protein-coding gene in the species Homo sapiens

type of keratin found in hair and nails

protein-coding gene in the species Homo sapiens