Keratin 85 (KRT85)

KRT85 is a member of the keratin gene family. As a type II hair keratin, it is a basic protein which heterodimerizes with type I keratins to form hair and nails. The predicted protein has 507 amino acids. The amino acid sequences of HB1, HB3, HB5, and HB6 are extremely conserved in the alpha-helical, N-terminal, and proximal C-terminal domains. In situ hybridization studies demonstrated that type II keratin genes are sequentially activated in the hair follicle in the following order: HB5--(HB1, HB3)--HB6. The onset of HB5 mRNA synthesis occurs immediately above a small population of matrix cells at the base of the hair bulb and in the trichocytes lining the dermal papilla. Synthesis extends upward through the matrix and ends in the lower part of the hair shaft cortex. The authors noted that the mRNA expression patterns of HB5 and HA5 are nearly identical.