title: Amino acid sequences of alpha-helical segments from S-carbosymethylkerateine-A. Complete sequence of a type-I segment.
abstract: The amino acid sequence of a type-I helical segment from the low-sulphur protein (S-carboxymethylkerateine-A) of wool was determined by combining automatic and manual-sequencing data. Whereas in the type-II helical segment most of the cationic groups occur in pairs, 11 of the 22 anionic residues in the sequence of the type-I segment were situated next to a second anionic residue. This suggests possible interactions between type-I and type-II helical segments in alpha-keratin. As observed with the sequence of a type-II helical segment a model constructed on 3.6 residues per turn of helix shows a line of hydrophobic residues along the helix, thereby supporting the physicochemical evidence that the molecule is predominantly helical and forms part of a coiled-coil structure. Examination of the sequence data by predictive methods indicates the possibilty of extensive sections of alpha-helix interspersed with discontinuities. The molecule contains a number of regions with peptide sequences identical with those found by other workers after enzymic digestion of fractions from oxidized wool.
mesh_terms: D000577:Amides / Q000032:analysis; D000595:Amino Acid Sequence; D002268:Carboxypeptidases; D002848:Chromatography, DEAE-Cellulose; D007633:Keratins; D010446:Peptide Fragments / Q000032:analysis / Q000302:isolation & purification; D014357:Trypsin; D014934:Wood
chemical_list: D000577:Amides; D010446:Peptide Fragments; D007633:Keratins; D002268:Carboxypeptidases; D014357:Trypsin