Component of the epidermal cornified cell envelopes. Found in keratohyalin granules of the granular cells of the epidermis. Embryonic skin. Highest level in the adult forestomach followed by the skin. Lower levels in the tongue, esophagus. Detected in the granular and cornified layers of the mature epidermis. First detected on gestational day 15.5 in the epidermis. Processed during the process of epidermal differentiation. Forms covalent cross-links mediated by transglutaminase TGM3, between glutamine and the epsilon-amino group of lysine residues (in vitro). Belongs to the S100-fused protein family. In the N-terminal section; belongs to the S-100 family.