Structural and topological studies of cholesteatoma proteins, in relation to the keratinization process.

For the extraction of soft keratins from bovine snout or human epidermis the best results were obtained with a detergent (sodium dodecyl sulphate, SDS) or hydrogen bond breaking agent (urea) in a reducing medium (2-mercaptoethanol, 2-ME). N-acetylcysteine was a little less effective. Keratins from both sources gave typical sets of protein bands with molecular weights between 40.000 and 70.000 daltons. Upon electrofocusing special precautions had to be taken to avoid reoxidation and reaggregation of protein subunits. Keratins from aural cholesteatomas were obtained by extraction with SDA and 2-ME, with N-acetylcysteine alone and to a lesser extent with urea and 2-ME. The pattern of these keratins on SDS-gel is less complicated than that obtained from human skin or bovine snout. Histophotometric results argue for a clear analogy between the nuclear DNA metabolism in normal skin epidermis and cholesteatoma matrix. The only differences of potential relevance are the much wider range of the nuclear DNA amount in cholesteatoma stratum basale cells compared with basal cells in normal epidermis, and the higher persistence of nuclear DNA in cholesteatoma stratum granulosum, indicating postponement of keratinocyte terminal differentiation.