Characterization of lead-binding protein in human serum

Abstract

Although lead is one of the most useful metals, it is also toxic for human. It may cause anemia and other serious symtoms. Biochemical mechanisms in lead poisoning is of interest. The studies about lead transportation, its binding and elimination may be utilized for prevention and treatment of Pb-poisoning. It is shown in this study with in vitro experiment that lead is taken up rapidly by human blood cells, reaches saturation within 8 min, leaving lead residues in the serum fraction. Furthermore, in the absence of plasma, blood cells take up lead but only 30% of that in the presence. This suggests the involvement of some factor(s) in serum in lead transportation. Lead is further observed to decrease the concentration of protein-bound iron in human serum, upon its attachment indicating that one of the factors involves in lead transportation may be transferrin, iron carrier protein. By Sephadex G-200 Column Chromatography with its molecular weight and Polya-crylamide Gel Electrophoresis pH 8.3, the lead-binding protein is confirmed to be transferrin. The stoichiometric study of Pb : Fe on transferring molecule is also study, but the result obtained is not yet conclusive due to too low the concentration of Pb utilized. Pb and Fe can shift band of transferrin in Isoelectric Focusing Polyacrylmide Gel Electrophoresis in the same fashion suggesting their similar binding. Pb can be removed from transferrin molecule by some chelators, CaNa₂EDTA, Dimercaprol and D-penicillamine, which reduce Pb bound about 88, 96 and 100%, respectively.