Keratin Keratin Keratin () is one of a family of fibrous structural proteins. It is the key structural material making up hair, horns, claws, hooves, and the outer layer of human skin. Keratin is also the protein that protects epithelial cells from damage or stress. Keratin is extremely insoluble in water and organic solvents. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and form strong unmineralized epidermal appendages found in reptiles, birds, amphibians, and mammals. The only other biological matter known to approximate the toughness of keratinized tissue is chitin. Keratin derives from Greek ' from '
Virulence-related outer membrane protein family invasion and helps defend against the complement system. Although OmpX has the same beta-sheet topology as the structurally related outer membrane protein A (OmpA) , their barrels differ with respect to the shear numbers and internal hydrogen-bonding networks. OspA from Borrelia burgdorferi is an unusual outer surface protein, it has two globular domains which are connected with a single-layer β-sheet. This protein is highly soluble, contains a large number of Lys and Glu residues. These high entropy residues may disfavor crystal packing. Virulence-related outer membrane protein family Virulence-related outer membrane proteins are expressed in Gram-negative bacteria and are essential to