KRTAP13-2 is a keratin-associated protein that functions in hair shaft structure. Based on limited published evidence, KRTAP13-2 is embedded within the interfilamentary matrix of hair cortex, where it cross-links with hair keratins through extensive disulfide bonding, contributing to hair shaft rigidity and resistance 1. In sheep, KRTAP13-2 variants show association with reduced fiber diameter variation and coefficient of variation in heterotypic fibers, suggesting a role in regulating fiber diameter uniformity 1. The protein localizes to the cytosol and mediates protein binding interactions.