Synthetic peptides corresponding to keratin subunits elicit highly specific antibodies

The presence of common antigenic determinants within all keratin proteins has made difficult the production of antisera which are monospecific for individual keratin subunits. Synthetic peptides corresponding to the carboxyl-terminal amino acid sequences of the mouse 59- and 67-kilodalton keratins were used to produce antibodies which were highly specific for these keratin subunits. This method of antibody production was chosen after examination of amino acid sequence data (which were deduced from the nucleotide sequence of cDNA clones for these and other mouse keratins) revealed that the carboxyl-terminal amino acid sequences of various keratins were unique. Indirect immunofluorescence staining of newborn-mouse skin with these antisera demonstrated that the 59- and 67-kilodalton keratins were only present within the differentiated cells of the epidermis (the suprabasal layers) and not in the undifferentiated cells (the basal layer). These results are consistent with our previous work concerning the expression of these keratin genes at the messenger RNA level (Roop, D. R., Hawley-Nelson, P., Cheng, C. K., and Yuspa, S. H. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 716-720). Data obtained with the antisera directed against the 67-kilodalton keratin also indicated that the carboxyl-terminal sequences of this subunit were not present in the nonliving layer (the stratum corneum) of the epidermis. This approach should be useful for the production of antisera specific for other keratin subunits as additional sequence information becomes available.