Copper transport: insights into a ceruloplasmin-based delivery system.
Ceruloplasmin binds to the membranes of K562 cells. The binding has been shown to result in a temperature-dependent transfer of ceruloplasmin-bound copper into the cytosol. Ascorbic acid (100 microM) stimulates the transmembrane transfer nearly 10-fold, depending on the initial concentration of 67Cu-ceruloplasmin. The protein moiety of ceruloplasmin does not enter the cells. Bathocuproine disulfonate, a chelator specific for cuprous copper, inhibits the uptake, suggesting copper atoms are reduced concomitant with their removal from ceruloplasmin. Cytosolic 67Cu from ceruloplasmin was found mainly bound to Cu, Zn superoxide dismutase, the major cytosolic copper protein in these cells. Evidence supporting the various phases in the ceruloplasmin-mediated transport mechanism are presented.
Harris
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Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843.
Percival
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D001205:Ascorbic Acid / Q000494:pharmacology; D001692:Biological Transport; D002478:Cells, Cultured; D002570:Ceruloplasmin / Q000378:metabolism*; D003300:Copper / Q000037:antagonists & inhibitors / Q000378:metabolism*; D003301:Copper Radioisotopes; D006427:Hemin / Q000494:pharmacology; D006801:Humans; D004915:Leukemia, Erythroblastic, Acute; D010618:Phenanthrolines / Q000494:pharmacology
D003301:Copper Radioisotopes; D010618:Phenanthrolines; D006427:Hemin; D003300:Copper; C002478:bathocuproine; D002570:Ceruloplasmin; D001205:Ascorbic Acid