The primary structure of feather keratins from duck ( Anas platyrhynchos) and pigeon ( Columba livia)

Abstract

The amino acid sequences of the main components, B-4, from feather barbs of duck ( Anas platyrhynchos) and pigeon ( Columba livia) were determined by manual Edman degradation of the tryptic peptides. The alignment of the peptides was achieved by comparison with the already known sequence of feather keratin from fowl ( Gallus gallus). The B-4 chains of duck and pigeon were found to consist of the same number of 95 amino acid residues (molecular weights of 10 168 and 10 167, respectively, in S-carboxymethylated forms). When the three sequences were compared, the amino acid residues of 82 positions were common (similarity of 85%). Most of them were localized in the central portion of the polypeptide chain. There were two replaced residues in the N-terminal region, but all the S-carboxymethylcysteine residues were conserved among the three species. These results support the authors' prediction that the central region, having a high hydrophobicity and favoring a β-sheet structure, is related to the formation of the structural framework of the microfibril and cysteine residues in the N-terminal region are important for the formation of feather structure (Arai, K.M., Takahashi, R., Yokote, Y. and Akahane, K. (1983) Eur. J. Biochem. 132, 501–507). The C-terminal region had a marked variation in amino acid sequence. The sequences have 14 substitutions of amino acid residue among three species; 8 of them were found between duck and pigeon, 9 between duck and fowl and 12 between pigeon and fowl.