The fibrous proteins of stratum corneum.

The proteins of cow snout stratum corneum can be extracted in part with Tris buffer, pH 9.0, containing 6 M urea. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis shows that about half the extracted material migrates as prekeratin when the extract is treated with both SDS and mercaptoethanol; only trace amounts of the proteins migrating as prekeratin are seen when SDS alone is used. The urea extract gives precipitin lines to an antibody against prekeratin. After exhaustive extraction with the Tris-urea buffer an additional amount of protein is solubilized by extraction with buffer containing mercaptoethanol. This extract shows an electrophoretic pattern similar but not identical to prekeratin. These results suggest that the stratum corneum contains fibrous proteins with different degrees of cross-linking. An analogous system has also been observed in human stratum corneum.