The Structural Basis for the Heterogeneity of Chick Down Feather Keratin

Abstract

The amino acid sequences of prominent tryptic peptides of unfractionated carboxymethylated down feather keratin were determined by the dansyl‐Edman procedure and their arrangement within the intact primary structure deduced by comparison with closely homologous components of emu and gull feather keratin. The presence of multiple amino acid interchanges in different down feather keratin chains was inferred. Most or all keratin chains possessed amino‐terminal and carboxyl‐terminal regions, rich in half cystine, and a large internal region devoid of half‐cystine and rich in hydrophobic amino acids. The size of all down feather keratin chains was conserved and the sequence data were compatible with all chains having the same number of amino acid residues.The amino acid substitutions reflected the presence in the chick genome of multiple keratin genes differing from one another by one or a few nucleotide changes.