Beta-keratin

Beta-keratin (β-keratin) is a member of a structural protein family found in the epidermis of reptiles, birds, and pangolins. It forms a substance that is rigid and waterproof, with different versions of the protein appearing in scales, claws, and feathers. It was considered a type of keratin because it is analogous to the keratin in mammals, but it is now instead considered a "beta-protein."