Structure of epidermal keratin and variations in its polypeptide composition.
The subunit structure of prekeratin has been studied by examining the products formed after proteolytic digestion and site-specific cleavage at cysteine and cystine residues. The monomer unit of prekeratin consists of 3 polypeptides which contain a helical segment of 34,000 daltons. This segment appears to consist of 2 helical polypeptides separated by a non-helical one, and the helical polypeptides in turn contain 2 smaller segments of about 7,000 daltons. Cysteine residues are not localized to one region of prekeratin, but are evenly distributed in the molecule; this suggests that they may be located in the nonhelical regions. The polypeptide composition of keratins has been studied by SDS polyacrylamide gel electrophoresis, and heterogeneity in the polypeptide components can be demonstrated between species, within a species, and in different areas of skin of a single member of species. The pattern of keratin polypeptides, furthermore, is not fixed but can be altered by changes in the cellular environment.
D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D003545:Cysteine / Q000378:metabolism; D003553:Cystine / Q000378:metabolism; D003599:Cytoskeleton / Q000648:ultrastructure*; D004817:Epidermis / Q000648:ultrastructure*; D006801:Humans; D007633:Keratins / Q000378:metabolism*; D008970:Molecular Weight; D009666:Nose; D010446:Peptide Fragments / Q000032:analysis; D011487:Protein Conformation; D011498:Protein Precursors / Q000378:metabolism
D010446:Peptide Fragments; D011498:Protein Precursors; C004818:prekeratin; D003553:Cystine; D007633:Keratins; D003545:Cysteine