Isolation of the polypeptide chains of prekeratin

Stratum corneum alpha protein, the principal structural protein of the epidermis, and its precursor prekeratin have been studied. Both proteins have similar patterns on sodium dodecyl sulfate electrophoresis and consist of several polypeptide chains (designated A, A', B, B'). These subunits have been isolated by chromatography on diethylaminoethyl cellulose in 8 M urea and characterized. Immunological studies have shown that the four subunits could be grouped into two distinct immunological groups referred to as the A and B groups and analysis of the cyanogen bromide fragments of purified components appeared to support such a hypothesis. X-ray diffraction studies have shown that at least one A component and one B component are necessary for the production of a typical alpha X-ray diffraction pattern. Circular dichroism studies have shown that the polypeptide chains of either class have low ellipticity when compared to the intact molecule, indicating that both chains are necessary for the formation of an alpha-helical structure.