keratin

keratin

keratin (kĕrˈətĭn), any one of a class of fibrous protein molecules that serve as structural units for various living tissues. The keratins are the major protein components of hair, wool, nails, horn, hoofs, and the quills of feathers. These proteins generally contain large quantities of the sulfur-containing amino acids, particulary cysteine. The helical keratin molecules twist around each other to form elongated strands called intermediate filaments. The formation of a covalent chemical bond called a disulfide bridge between the sulfer atoms on two cysteins on separate polypeptide chains of keratin allows for the cross-linkage of these chains and results in a fairly rigid aggregate. This phenomenon is seen to be consistent with the physiological role of the keratins, which provide a tough, fibrous matrix for the tissues in which they are found. Human hair is approximately 14% cystine (cysteins cross-linked by disulfide bridges).

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keratin

[′ker·əd·ən]

(biochemistry)

Any of various albuminoids characteristic of epidermal derivatives, such as nails and feathers, which are insoluble in protein solvents, have a high sulfur content, and generally contain cystine and arginine as the predominating amino acids.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

keratin

A proteinaceous material used as a retarder for plaster.

McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc.

keratin

, ceratin

a fibrous protein that occurs in the outer layer of the skin and in hair, nails, feathers, hooves, etc.

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005