Involucrin in the epidermal cells of subprimates

The protein involucrin is a precursor of the cross-linked envelope that forms during terminal differentiation of the keratinocyte. Most of the human involucrin molecule consists of a segment of homologous repeats of a sequence of 10 amino acids. A similar segment is present in the involucrin of other higher primates, but not in lower animals. We show here that the older part of the involucrin molecule (the ancestral segment) is present in the epidermal cells of subprimates. This has been demonstrated with antisera prepared against different peptides of the ancestral segment of the human protein. No single antiserum detects involucrin of all subprimate species, but probably all involucrins can be detected using antiserum against some sequence in the ancestral segment. Although the involucrin gene has been extensively remodeled in higher primates, its origins extend lower in the animal kingdom.