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Complete amino acid sequence of a histidine-rich proteolytic fragment of human ceruloplasmin.

  • I B Kingston
  • B L Kingston
  • F W Putnam
Publication Date
Apr 01, 1979
  • Biology
  • Design


The complete amino acid sequence has been determined for a fragment of human ceruloplasmin [ferroxidase; iron(II):oxygen oxidoreductase, EC]. The fragment (designated Cp F5) contains 159 amino acid residues and has a molecular weight of 18,650; it lacks carbohydrate, is rich in histidine, and contains one free cysteine that may be part of a copper-binding site. This fragment is present in most commercial preparations of ceruloplasmin, probably owing to proteolytic degradation, but can also be obtained by limited cleavage of single-chain ceruloplasmin with plasmin. Cp F5 probably is an intact domain attached to the COOH-terminal end of single-chain ceruloplasmin via a labile interdomain peptide bond. A model of the secondary structure predicted by empirical methods suggests that almost one-third of the amino acid residues are distributed in alpha helices, about a third in beta-sheet structure, and the remainder in beta turns and unidentified structures. Computer analysis of the amino acid sequence has not demonstrated a statistically significant relationship between this ceruloplasmin fragment and any other protein, but there is some evidence for an internal duplication.

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