期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：12
页码：5377-5381
DOI：10.1073/pnas.74.12.5377
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Nine samples of human ceruloplasmin [iron(II):oxygen oxidoreductase; EC 1.16.3.1 ] prepared by different procedures have been examined for heterogeneity; gel electrophoresis showed that seven contained a number of components with molecular weights ranging from 20,000 to 130,000, and two contained largely a single component of molecular weight 130,000. Digestion of a single-component preparation with plasmin produced fragments with molecular weights similar to those found in the multicomponent preparations. Amino-terminal analysis, peptide mapping, and amino acid analysis showed that plasmin digestion generated a fragment of 20,000 molecular weight, which corresponded to a component present in a multicomponent ceruloplasmin preparation. The 20,000 molecular weight fragment appears to correspond to the so-called alpha-subunit or L-chain of human ceruloplasmin. Chemical evidence is thus provided that ceruloplasmin is a single-chain protein and that the so-called subunits are fragments. The 20,000 molecular weight fragment contains a single cysteine; amino acid sequence studies have shown that the sequence in the vicinity of this residue is similar to that around the single cysteine residue in plant plastocyanins and bacterial azurins, which are small, blue, copper-containing proteins.
