Keratin 6A assembled hard keratins to form a more structurally resilient material. Both epithelial keratins and hard keratins can be further subdivided into type I (acidic) keratins and type II (neutral-basic) keratins. The genes for the type I keratins are located in a gene cluster on human chromosome 17q, whereas the genes for type II keratins are located in a cluster on human chromosome 12q (the exception being K18, a type I keratin located in the type II gene cluster). Keratin 6A (protein name K6A; gene name "KRT6A"), is a type II cytokeratin, one of a number of isoforms of keratin 6
Alpha-keratin must be type I, while the other must be type II. Even within type I and II, there are acidic and basic keratins that are particularly complementary within each organism. For example, in human skin, K5, a type II alpha keratin, pairs primarily with K14, a type I alpha-keratin, to form the alpha-keratin complex of the epidermis layer of cells in the skin. Hard alpha-keratins, such as those found in nails, have a higher cysteine content in their primary structure. This causes an increase in disulfide bonds that are able to stabilize the keratin structure, allowing it to resist a