(keratin) Family of cystine-rich proteins that tend to aggregate in side-to- side fashion, forming tough filaments or sheets; main constituent of intermediate filaments in epidermal tissues.

(keratins) A class of fibrous proteins or scleroproteins that represents the principal constituent of EPIDERMIS; HAIR; NAILS; horny tissues, and the organic matrix of tooth ENAMEL. Two major conformational groups have been characterized, alpha-keratin, whose peptide backbone forms a coiled-coil alpha helical structure consisting of TYPE I KERATIN and a TYPE II KERATIN, and beta-keratin, whose backbone forms a zigzag or pleated sheet structure. alpha-Keratins have been classified into at least 20 subtypes. In addition multiple isoforms of subtypes have been found which may be due to GENE DUPLICATION.

Cytokeratins are a family of cysteine-rich fibrous structural proteins that form tough filaments or sheets. These proteins are the main component of intermediate filaments in the epidermis, hair, nails, horny tissues, and the organic matrix of tooth enamel.

Keratin, fibrous structural protein of hair, nails, horn, hoofs, wool, feathers, and of the epithelial cells in the outermost layers of the skin. Keratin serves important structural and protective functions, particularly in the epithelium. Some keratins have also been found to regulate key cellular...