a type I cytoskeletal keratin. The keratins are intermediate filament proteins responsible for the structural integrity of epithelial cells and are subdivided into cytokeratins and hair keratins. Keratin 19 differs from all other IF proteins in lacking the C-terminal tail domain. Unlike its related family members, this smallest known acidic cytokeratin is not paired with a basic cytokeratin in epithelial cells. It is specifically expressed in the periderm, the transiently superficial layer that envelopes the developing epidermis. Note: This description may include information from UniProtKB.