Soluble proteins from fowl feather keratin. I. Fractionation and properties

A method is described for the fractionation of reduced and alkylated proteins of fowl feather. Fowl feather extracts were chromatographed on a Sephadex G-75 column in 4 M urea containing 1 M NaCl and separated into four fractions, GF-1, 2, 3, and 4. The elution patterns were used to compare the components of different feather parts, barbs, rachis + medulla, and calamus. In all cases, GF-3 was the main fraction and the percentages with respect to the total peak area found for barbs, rachis + medulla, and calamus were about 65%, 74%, and 93%, respectively. Each of the fractions was examined by polyacrylamide disc gel electrophoresis and all were heterogeneous. The slowly moving bands mainly corresponded to fraction GF-1, intermediate bands to GF-2 and 3, and faster bands to GF-4. Many other polypeptide chains, which have not been found previously, were newly separated from three minor fractions of fowl body feather. The molecular weights of fractions GF-2 and 3 were estimated by calibrated gel filtration to be 33,000 and 10,500, respectively. Marked differences were found in the amino acid compositions of various fractions from fowl feather. The GF-1 fraction and insoluble residue had very similar compositions; in both cases the contents of serine, glycine, and proline were lower and those of helix-favoring amino acids, namely, lysine, tyrosine, and methionine, were higher than those found in other fractions.