[Isolation, composition, and physicochemical properties of 9 peptides released by the action of cyanogen bromide on human serotransferrin].

Cyanogen bromide-cleaved human serotransferrin (STF) is separated by gel filtration with "Sephadex G 75" into 4 fractions (CN-A to CN-D) which are subfractionated by combining "DEAE-Sephadex" chromatography, gel filtration and paper electrophoresis. 9 peptides are obtained: from fraction CN-A, 2 glycopeptides (CN-5 and CN-6); from fraction CN-C, a single cystine-free peptide (CN-7); from fraction CN-D, 2 small peptides (CN-8 and CN-9). These results are in good agreement with the presence of 8 methionine residues in STF. Molecular weights, amino-acid and carbohydrate compositions of the 9 peptides are determined as well as their N-terminal and C-terminal amino acids. The largest fragment, glycopeptide CN-1 is derived from the C-terminal part of STF and peptide CN-6 from the N-terminal part. These results are the first step towards a complete amino-acid sequence determination of human serotransferrin.