Keratin 5, also known as KRT5, K5, or CK5, dimerizes with keratin 14 and forms the intermediate filaments(IF) that make up the cytoskeleton of basal epithelial cells. This protein is involved in several diseases including epidermolysis bullosa simplex and breast and lung cancers. Keratin 5(and K14) are expressed primarily in basal keratinocytes in the epidermis, specifically in the stratified epithelium lining the skin and digestive tract. Keratin intermediate filaments make up the cytoskeletal scaffold within epithelial cells, which contributes to the cell architecture and provides the cells with the ability to withstand mechanical, and non-mechanical, stresses. K5/K14 keratin pairs are able to undergo extensive bundling due to the non-helical tail of K15 acting as a weak cross-linker at the intermediate filament surface. This bundling increase the elasticity, and therefore the mechanical resilience, of the intermediate filaments.