A Novel Protein of Rat Epidermis —Haematoxylin Stain‐Positive Protein of Keratohyalin Granules as the Membrane Lining Protein of the Stratum Corneum—

A novel protein, haematoxylin stain‐positive, non‐nucleoprotein has been extracted from the epidermis of 3‐day‐old rats. This protein was purified through preparative isoelectric focusing, followed by sodium dodecylsulfate polyacrylamide gel electrophoresis. The purified protein had a molecular weight of 14,500 daltons and an isoelectric point of 4.7. The amino acid composition included 15% glycine, 11% serine, 13% glutamic acid and 10% aspartic acid, but only 1.9% histidine. Using the immunofluorescent and immunoelectron microscopic techniques, observation showed that the antibody formed as a result of purified antigen was located on keratohyalin granules and in the cell membrane of the stratum corneum of the skin. This haematoxylin stain‐positive protein could be synthesized in the stratum granulosum as one component of keratohyalin granules, coat the stratum corneum cell membrane and perhaps, we think, may act as one important component of the epidermal barrier.