Structure and expression of genes for a class of cysteine-rich proteins of the cuticle layers of differentiating wool and hair follicles.

The study characterized two evolutionarily conserved genes encoding ultra-high-sulfur (UHS) keratin proteins, one from human hair follicles and one from sheep wool follicles. These proteins, each 16 kD and containing over 50 cysteine residues, were identified as being highly cysteine-rich (31-36 mol%) and composed mainly of cysteine-rich and glycine-rich repeats. The genes were expressed specifically in the hair cuticle at a late stage of follicle development, as shown by tissue in situ hybridization. Genomic analysis revealed that these UHS keratin proteins are encoded by related multigene families in both human and sheep genomes.