Talk:Keratin

Minor edit

I removed the text saying "as are the claws of other animals and human fingernails", which came after the reference to alpha helix keratins being contained in nails and claws. Redundant. 201.238.95.208 14:27, 6 February 2007 (UTC)

Removed description of molecule

This text was removed; it needs more work before it goes back into the article:

Keratin molecules are helical and fibrous, twisting around each other to form strands called intermediate filaments. These proteins contain a high percentage of sulfur-containing amino acids, largely cysteine, which form disulfide bridges between the individual molecules resulting in a fairly rigid structure. Human hair is approximately 14% cysteine.

I wasn't the one who removed it, and don't have time to fix it yet; any takers?--maveric149

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Re the discussion about whether keratin is present in teeth, see this http://www.rush.edu/worldbook/articles/011000a/011000006.html from the World Book Medical Encyclopedia - keratin is a primary component of tooth enamel.

If there are disputes about facts, some references would be nice as a way of resolving arguments. Graham Chapman

Picture Link

That external link is just a picture of a polypeptide alpha helix.

While I am not a hair expert, I believe that the designations "hard" (applying to the keratin produced by trichilemmal keratinization in the hair cortex) as opposed to "soft" keratin (applying to the keratin produced for example by the inner root sheath) are standard. Please correct me if I am wrong.

>>I updated this section to include the current nomenclature - they're not called hard and soft anymore - but have not done a complete job of describing them, either. Will return if no one beats me to it. —Preceding unsigned comment added by Radcen (talk • contribs) 16:38, 3 November 2008 (UTC)

questions

"soft epithelial keratins, the cytokeratins, and harder hair keratins"

Is it constructive to correctly define keratins as being proteins and then say that some keratins are "soft" and some are "harder"? You could say that some keratins function in "soft" living epithelia while other keratins are found harder structures composed of dead cells.

>>No - the keratin proteins themselves are similar, whether they will remain in a celluar cytoplasm and function in a living cell or if their expression preceedes cornification. radcen (talk) 16:41, 3 November 2008 (UTC)

Classification needs to be updated

According to Wiley encyclopedia of molecular biology: "There are three groups of keratins: the a-keratins, the b-keratins, and the feather keratins (1, 2). The a-keratins can be subdivided into (i) the hard a-keratins of hair, nails, claws, beaks, quills, hooves, baleen, and horns and (ii) the (soft) epidermal or cytokeratins of the stratum corneum, corns, and calluses. The b-keratins are derived from the a-keratins as a result of pressure and temperature, and consequently do not represent an in vivo structure. Feather keratins are found in feathers and scales and in parts of claws and beaks." So the definition of b keratin needs to be modified to specify that they are derived from a keratins. --Dr.saptarshi 04:59, 21 February 2007 (UTC)

It depends on how you look at it. From a purely chemical point of view, the feather keratins consist primarily of beta-sheets, and so should be classified as beta-keratins. So's also silk fibroin. Where they occur in living organisms is another matter--but what does it have to do with the internal structure? Leokor (talk) 06:08, 25 February 2008 (UTC)