Keratin 5 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 increases the elasticity, and therefore the mechanical resilience, of the intermediate filaments. K5/K14 intermediate filaments are anchored to the desmosomes of basal cells via desmoplakin and plakophilin-1, connecting the cells to their neighbours. At the hemidesmosome, plectin and BPAG1 associate with transmembrane proteins α6β4 integrin, a type of cell adhesion molecule, and BP180/collagen XVII, linking K5/K14 filaments in the basal cells to the basal lamina. Epidermolysis
Beta-keratin whose flight capabilities have been questioned, would have had avian, but not feather, β-keratins. The small alvarezsaurid dinosaur "Shuvuuia deserti" shows evidence of a featherlike skin covering. Analysis by Schweitzer "et al." (1999) showed that these featherlike structures consisted of beta-keratin. There are two main forms of keratin, alpha-keratin and beta-keratin. Alpha-keratin is seen in humans and other mammals, beta-keratin is present in birds and reptiles. Beta-keratin is harder than alpha-keratin. Structurally alpha-keratin have alpha-helical coiled coil structure while beta-keratin have twisted beta sheet structure.bIn the case of β-sheets, this allows sterically-unhindered hydrogen bonding between the amino and carboxyl groups