Isolation, characterization and comparison of mammalian epidermal prekeratins.

1. The lower living layers of mammalian epidermis contain a cytoplasmic tonofilament protein, prekeratin, believed to be the precursor of the keratin which is found in the outer dead cell layer or stratum corneum. 2. Prekeratin is distinguished by its property of being extractable from epidermis homogenized in the presence of citric acid trisodium citrate buffer pH 2.65. 3. In the present study we have compared the epidermal prekeratins from ten mammalian species and have shown them to be of similar amino acid composition. 4. Conditions have been established for studying the immunology of these insoluble proteins and examination of their immunological properties has shown that they are similar to one another but that their antigenic determinants are different from those of callus keratin. 5. The SDS polyacrylamide gel electrophoretic patterns of these proteins differ widely and we have also demonstrated anatomical site variation by this method.