In the hair cortex, hair keratin intermediate filaments are embedded in an interfilamentous matrix, consisting of hair keratin-associated proteins (KRTAP), which are essential for the formation of a rigid and resistant hair shaft through their extensive disulfide bond cross-linking with abundant cysteine residues of hair keratins. The matrix proteins include the high-sulfur and high-glycine-tyrosine keratins. Interacts with hair keratins. Expressed in the upper portion of the hair cortex. Belongs to the KRTAP type 7 family. The sequence of 1-36 of PubMed:12359730 has not been submitted.