Amino acid sequences of α-helical segments from S-carboxymethylkerateine-A. Complete sequence of a type-II segment

Abstract

The helical fragments obtained by partial chymotryptic digestion of S-carboxymethylkerateine-A, the low-S fraction from wool, were fractionated into type-I and type-II helical segments in aqueous urea under conditions limiting carbamoylation. The amino acid sequence of a 109-residue type-II segment was completed by using the sequenator. When the data were incorporated into a helical model of 3.6 residues per turn the hydrophobic residues generated a band aligned at a slight angle to the helical axis. This result was in accord with the postulated coiled-coil structure of the crystalline regions of .alpha.-keratin.