Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of proteins of newbonr rat skin. II. Keratohyalin and stratum corneum proteins.

Keratohyalin extracts from newborn rat epidermis were prepared by potassium phosphate and citric acid-detergent extraction procedures. These preparations were compared by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis and amino acid analysis. The major band of the potassium phosphate extract has a molecular weight of 48,000. The major bands of the citric acid-detergent preparation have molecular weights of 64,000, 61,500, 57,000 and 54,000. Electrophoresis of S-carboxylmethylated (SCM)-fibrous protein results in two major bands of approximately 57,000 and 64,000. SDS gels of the two preparations of keratohyalin and the SCM-fibrous protein were compared with gels of the insoluble proteins of granular and eluted cornified cells. All of the major bands in the preparations of keratohyalin can be seen in gels of the granular preparation. The two SCM-fibrous protein bands correspond with two prominent bands in gels of the cornified cell preparation. Two bands of the citric acid-extracted keratohyalin sample also have the same mobility. The major band of the potassium phosphate-extracted preparation of keratohyalin corresponds with a third prominent band of the cornified cell preparation. These results suggest that biochemical components of the preparations of keratohyalin are present in both the granular and the cornified layers of newborn rat epidermis.