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Copper(II)-binding Ability of Human -Fetoprotein¹

Department of Biochemistry [Y. A., T. I.] and the Third Division, Department of Internal Medicine [F. I.], Niigata University School of Medicine, 757 Asahimachi-Dori 1-Bancho, Niigata, 951 Japan

The copper(II)-binding ability of human -fetoproteins, which were purified from umbilical cord serum and from ascites fluid of a hepatoma-bearing patient, was examined by equilibrium dialysis and gel filtration methods. The pH dependence of the copper(II)-binding ability of -fetoprotein was quite similar to that of albumin. -Fetoprotein bound 1 mol of copper(II) ion per mol of protein above pH 6.0 and 0.5 mol of copper(II) ion at pH 5.4, which is close to the pK value of the imidazole group of histidine. Photooxidation of -fetoprotein in the presence of methylene blue resulted in the loss of the copper(II)-binding ability of the protein in parallel with the destruction of the histidyl residues. A synthetic amino-terminal undecapeptide of -fetoprotein also bound copper(II) ion. These results indicate that the histidyl residue at the aminoterminal region of -fetoprotein plays an important role in the copper(II)-binding ability of the protein.

¹ This study was supported in part by a Grant-in-Aid from the Niigata University Science Foundation.

² To whom requests for reprints should be addressed, at Department of Biochemistry, Niigata University School of Medicine, 757 Asahimachi-Dori 1-Bancho, Niigata, 951 Japan.

Received 3/23/78. Accepted 7/18/78.