title: Filamentous Structure of Hard β-Keratins in the Epidermal Appendages of Birds and Reptiles.
abstract: The structures of avian and reptilian epidermal appendages, such as feathers, claws and scales, have been modelled using X-ray diffraction and electron microscopy data, combined with sequence analyses. In most cases, a family of closely related molecules makes up the bulk of the appendage, and each of these molecules contains a central β-rich 34-residue segment, which has been identified as the principal component of the framework of the 3.4 nm diameter filaments. The N- and C-terminal segments form the matrix component of the filament/matrix complex. The 34-residue β-rich central domains occur in pairs, related by either a parallel dyad or a perpendicular dyad axis, and form a β-sandwich stabilized by apolar interactions. They are also twisted in a right-handed manner. In feather, the filaments are packed into small sheets and it is possible to determine their likely orientation within the sheets from the low-angle X-ray diffraction data. The physical properties of the various epidermal appendages can be related to the amino acid sequence and composition of defined molecular segments characteristic of the chains concerned.
authors.affiliation: Institute of Fundamental Sciences, Massey University, Private Bag 11-222, Palmerston North, 4442, New Zealand.|, 28 Satinay Drive, Noosa Parklands, Tewantin, Qld, 4565, Australia.
authors.forename: R D Bruce
authors.initials: RD
authors.lastname: Fraser
authors.affiliation: Institute of Fundamental Sciences and Riddet Institute, Massey University, Private Bag 11-222, Palmerston North, 4442, New Zealand. d.parry@massey.ac.nz.
authors.forename: David A D
authors.initials: DA
authors.lastname: Parry
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001717:Birds; D004817:Epidermis / Q000737:chemistry* / Q000648:ultrastructure; D005241:Feathers / Q000737:chemistry / Q000648:ultrastructure; D006724:Hoof and Claw / Q000737:chemistry / Q000648:ultrastructure; D011487:Protein Conformation; D012104:Reptiles; D017386:Sequence Homology, Amino Acid; D014961:X-Ray Diffraction; D053800:beta-Keratins / Q000737:chemistry* / Q000648:ultrastructure
chemical_list: D053800:beta-Keratins
keywords: Archosaurs; Feather keratin X-ray pattern; Filament packing in feather; High-glycine-tyrosine proteins; Mechanical properties of β-keratins; Squamates