Nematodes and many other non-chordate animals seem to have only type VI intermediate filaments, fibers that structure the nucleus. Keratins (also described as cytokeratins) are polymers of type I and type II intermediate filaments that have been found only in chordates ( vertebrates, amphioxus, urochordates). The new term corneous beta protein (CBP) has been proposed to avoid confusion with α-keratins. Recent scholarship has shown that sauropsid β-keratins are fundamentally different from α-keratins at a genetic and structural level. The baleen plates of filter-feeding whales are made of keratin. However, beta sheets are also found in α-keratins. These keratins are formed primarily in beta sheets. They are found in the nails, scales, and claws of reptiles, in some reptile shells ( testudines, such as tortoise, turtle, terrapin), and in the feathers, beaks, and claws of birds. The harder beta-keratins (β-keratin)s are found only in the sauropsids, that is all living reptiles and birds. These antibodies are used as fluorescent markers to distinguish subsets of mouse thymic epithelial cells in genetic studies of the thymus. For example, mouse thymic epithelial cells react with antibodies for keratin 5, keratin 8, and keratin 14. They are also present in epithelial cells in general. Keratin filaments are abundant in keratinocytes in the hornified layer of the epidermis these are proteins which have undergone keratinization. They form the hair (including wool), the outer layer of skin, horns, nails, claws and hooves of mammals, and the slime threads of hagfish. The horns of the impala are made of keratin covering a core of bone.Īlpha-keratins (α-keratins) are found in all vertebrates. Spider silk is classified as keratin, although production of the protein may have evolved independently of the process in vertebrates. Keratin comes in two types, the primitive, softer forms found in all vertebrates and harder, derived forms found only among sauropsids (reptiles and birds). The only other biological matter known to approximate the toughness of keratinized tissue is chitin. Excessive keratinization participate in fortification of certain tissues such as in horns of cattle and rhinos, and armadillos' osteoderm. 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. Keratin is extremely insoluble in water and organic solvents. Keratin also protects epithelial cells from damage or stress.
#Translucent cells containing keratin skin#
It is the key structural material making up scales, hair, nails, feathers, horns, claws, hooves, and the outer layer of skin among vertebrates. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. Keratin ( / ˈ k ɛr ə t ɪ n/ ) is one of a family of structural fibrous proteins also known as scleroproteins. Microscopy of keratin filaments inside cells