KRT31Keratin, type I cuticular Ha1 is a protein that in humans is encoded by the KRT31 gene.FunctionThe protein encoded by this gene is a member of the keratin gene family. As a Type I hair keratin, it is an acidic protein which heterodimerizes with type [II keratin]s to form hair and nails. The type I hair keratins are clustered in a region of chromosome 17q21.2 and have the same direction of transcription.