The Structure of Human Trichohyalin: Potential Multiple Roles as a Functional EF-Hand-Like Calcium-Binding Protein, a Cornified Cell Envelope Precursor, and an Intermediate Filament-Associated (Cross-Linking) Protein

The study on human trichohyalin revealed that it potentially served multiple roles in hair follicle and epidermal cells. Trichohyalin, a 248 kDa protein, was associated with keratin intermediate filaments (KIF) and was a substrate for transglutaminases. It was characterized by a high content of charged residues and several alpha-helical domains, which facilitated its function as a KIF-associated protein by cross-linking filaments. The protein's structure suggested it acted as an elongated flexible rod, possibly contributing to the cell envelope's organization alongside involucrin. Additionally, trichohyalin contained EF-hand-like calcium-binding domains, indicating a role in calcium-dependent processing during cell differentiation.