The Complete Amino Acid Sequence of a Feather Keratin From Emu (Dromaius Novae-Hollandiae)

Abstract

The complete amino acid sequence of one of the two major components comprising the rachis and calamus of emu (D. novae-hollandiae) feather keratin has been determined. The molecule consists of 102 amino acids and has a molecular weight (in the S-carboxymethyl form) of 10,459. The half-cystine residues are located towards either end of the molecule. There is an insoluble tryptic peptide of 65 residues, T3, in which the hydrophobic residues Val, Leu, and He are preferentially placed and this section also contains most of the Ser and Gly residues of the molecule. It is the T3 section which contains the crystalline part of the molecule. Comparison of the sequence with peptides isolated by Schroeder et al. (1957) from calamus from turkey feather suggests that the T3 section in both feathers could be very similar. The proline residues are not regularly distributed. The N-terminal sequence, NAc-Ser-SCMCys-Tyr is the same as that found previously in goose (Anser domesticus) feather calamus.

Molecular packing in the feather keratin filament

“…Amino acid sequences for avian keratins were taken from the following publications: emu (Dromaius novaehollandiae) feather (O'Donnell, 1973), seagull (Larus novaehollandiae) feather (O'Donnell and Inglis, 1974), chicken (Gallus domesticus) feather (Walker and Rogers, 1976), duck (Anas platyrhynchos) and pigeon (Columba livia) feather, (Arai et al, 1986), turkey vulture (Cathartes aura) keratin (Sawyer et al, 2003), wood stork (Mycteria americana) keratin (Sawyer et al, 2003), and chicken (Gallus domesticus) scale (Walker and Bridgen, 1976). Amino acid sequences for reptilian keratins were taken from the following: lizard (Varanus varius) claw (Inglis et al, 1987), lizard (Podarcis sicula) keratin proteins (Valle et al, 2007), gecko (Tarentola mauritanica) skin protein components (Toni et al, 2007a,b), and snake (Elaphe guttata) keratin proteins (Valle et al, 2007).…”

“…Avian feathers have a filament-matrix texture (Filshie and Rogers, 1962) and the bulk of the rachis is composed of a single protein with a molecular weight of about 10 kDa (O'Donnell, 1973;O'Donnell and Inglis, 1974). The feather keratin molecule contains a 32-residue segment that is believed to form the framework of the filament (Fraser and MacRae, 1976) and a segment of similar composition is found in keratin proteins isolated from chicken leg scales (Walker and Bridgen, 1976), and lizard claws (Inglis et al, 1987) and skin (Toni et al, 2007a,b), even though the molecular weights and overall compositions of these materials are markedly different.…”

The structural basis of the two-dimensional net pattern observed in the X-ray diffraction pattern of avian keratin

“…4a and the Fraser and Parry (2011) as the unit of secondary structure common to avian and reptilian hard keratins (view down the aaxis). The numbering corresponds to the sequence in emu feather (O'Donnell, 1973). (b) The b-sheet portion of (a).…”

“…Following the determination of the amino acid sequences of emu and seagull feather proteins (O'Donnell, 1973;O'Donnell and Inglis, 1974) it was shown that part of the molecule contained out-of-phase eight-residue periodicities in the propensities of residues to exist in either a b-conformation (b-potential) or in a b-turn (b-turn potential). It was therefore suggested that the b-sheet in the feather keratin filament consisted of a regularly folded chain with five strands (Fraser and MacRae, 1976).…”

Keratin Protein-Catalyzed Nitroaldol (Henry) Reaction and Comparison with Other Biopolymers

“…Keratins contain a central~310 residue domain with four segments in α-helical conformation that are separated by three short linker segments in β-turn conformation [3]. The complete amino acid sequence of keratins obtained from different sources has been reported in several publications [4][5][6][7], making the protein a suitable candidate to be tested as a catalyst. Recently, keratinous materials have attracted increasing attention as an important source of renewable biomaterials, especially since keratin wastes have been estimated to be more than 5 million tons per year [8], being used after degradation for different applications including scaffolds for tissue engineering [9,10] and support matrices for catalytic metal nanoparticles [11], among others [12].…”