title: Amino acid sequences of alpha-helical segments from S-carboxymethylkerateine-A. Tryptic and chymotryptic peptides from a type-II segment.
abstract: 1. Amino acid-sequence studies were done on a peptide of mol.wt. approx. 12500 that was isolated from the highly helical fragments obtained by partial chymotryptic digestion of the low-sulphur proteins (S-carboxymethylkerateine-A) from wool. 2. The peptides obtained by tryptic and chymotryptic digestion of this large peptide were separated by ion-exchange chromatography on DEAE-cellulose at pH8.5 with an (NH4)(2)CO(3) concentration gradient and, where necessary, purified further by paper electrophoresis. 3. Determination of the sequences of many of these peptides showed that a high proportion of the cationic residues occurs in pairs. 4. Although two of the four S-carboxymethylcysteine residues are located in what appears to be a non-helical region near the N-terminus the other two S-carboxymethylcysteine residues occur in or near sequences suggesting a helical conformation. 5. Some peptides were obtained, in low yields, that appeared to be homologues of more major ones. These suggest either homologies in the helical portions of the low-sulphur proteins or the presence of closely related amino acid sequences in helical regions of completely different origins. 6. A partial sequence of the complete peptide is proposed.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002852:Chromatography, Ion Exchange; D002918:Chymotrypsin; D004590:Electrophoresis, Paper; D007633:Keratins; D010446:Peptide Fragments / Q000032:analysis; D014357:Trypsin; D014935:Wool
chemical_list: D010446:Peptide Fragments; D007633:Keratins; D002918:Chymotrypsin; D014357:Trypsin