Comparative Binding Studies of Aluminum and Iron to Serum Transferrin

The binding characteristics of aluminum and iron to serum transferrin were investigated and compared by using spectrophotometric titration technique. Both metal ions bound to serum transferrin and competed for the same binding sites on the transferrin. Aluminum transferrin (Al-tf) and iron transferrin (Fe-tf) complexes had maximum absorbances at 240 nm and 470 nm respectively. Bicarbonate was necessary for binding activities and citric acid facilitated the binding of both metals to transferrin. Tyrosyl residues were involved in iron binding but not in aluminum binding to transferrin. The complete saturation of transferrin with iron or aluminum was performed within 30 mins. Iron uptake by transferrin was reduced in the presence of aluminum. The relationship between aluminum and iron binding to this protein and the occurrence of anemia in hemodialyzed patients is discussed.