Comparative studies of the marginal band and plasma membrane of the epidermis.
The membranous fraction isolated from stratum corneum by 8M urea-beta ME containing alkaline buffer (pH 9.0) is quite crude when observed by electron microscopy. However, this procedure may be useful for clinical samples, as one can isolate and compare both the soluble (interfilamentous) fraction and the keratin filament from the same sample in addition to the residues (membranous fraction). A further purified membranous fraction was isolated by a new method. Human stratum corneum was chopped and treated with 8M urea-50 mM Tris-HCl (pH 9.0), digested by the use of trypsin, and the product fractionated by a sucrose density gradient to obtain separate single cells without the cytoplasm. One sample was then treated with trypsin for 1 hour and another with urea buffer for 24 hours. Observations revealed a thickened inner membrane (marginal band) of approximately 150A. Each of the membranous samples contained a level of half-cystine markedly higher in amount (around 100/1,000) and involved mostly in the epsilon-(gamma-glutamyl) lysine cross-linkages (around 30%). In order to compare the membranous fraction of horny and living cells (marginal bands and plasma membranes), the fraction was then isolated from living cells. The relative amino acid composition of the membranous fraction of the plasma membrane resembled that of human erythrocytes, but was quite different from that of the marginal band. These comparative studies of biochemical and morphological features suggested the importance of S-S cross-linking enzymes and transglutaminase in the transformation mechanism of the marginal band.
D000596:Amino Acids / Q000032:analysis; D002462:Cell Membrane / Q000032:analysis / Q000201:enzymology; D004817:Epidermis / Q000032:analysis / Q000648:ultrastructure*; D006651:Histocytochemistry; D006801:Humans; D006868:Hydrolysis; D008297:Male; D010447:Peptide Hydrolases; D013194:Staining and Labeling; D014357:Trypsin; D014508:Urea / Q000031:analogs & derivatives
D000596:Amino Acids; D014508:Urea; D010447:Peptide Hydrolases; D014357:Trypsin