Characterization of keratin polypeptides of normal and psoriatic horny cells.

Keratin was extracted from normal human horny cells of the leg, calluses of the sole, and psoriatic scales. After dissociation in sodium dodecyl sulfate the polypeptides were separated by Laemmli's gel electrophoresis method and their molecular weights and relative amounts determined. Normal horny cells contained 3 polypeptide chains of Mr 67K, 59K, and 57K, while those of callus contained 9 polypeptides of Mr 67K, 66K, 63K, 62K, 58K, 54K, 52K, 48K, and 45K. In both cases all keratin polypeptides participated in filament reassembly in vitro and were recovered from the filaments. In psoriatic scale keratin, 7 prominent polypeptides were detected having Mr 67K, 59K, 57K, 50K, 48K, 42K, and 40K. The 67K polypeptide could not be recovered from reassembled filaments. Ultrastructural studies revealed that these filaments are imperfect and readily aggregate into thick fibrils. These observations indicate that there are significant differences in composition of keratin of normal horny cells, calluses, and psoriatic scales.