AN IN-VITRO STUDY ON THE BINDING OF AL(III) TO HUMAN SERUM TRANSFERRIN WITH THE ISOELECTRIC-FOCUSING TECHNIQUE

Transferrin saturated with Al3+ subjected to isoelectric focusing (IEF ) in a pH gradient can be separated into four fractions, representing the apotransferrin, transferrin with aluminum at the metal binding sit e in the C- or N-terminal lobe, or both, The electrophoretic mobilitie s of these four fractions are identical to those of the iron-transferr in counterparts, Simultaneous binding of aluminum and iron to transfer rin can also be demonstrated. The decreased saturation after IEF indic ates that the affinity of transferrin for aluminum is low compared wit h its affinity for iron, This effect is particularly evident when bica rbonate is used as the synergistic anion in the loading procedure, In contrast, loading of transferrin with aluminum in the presence of oxal ate produces a di-aluminum-transferrin complex that is stable during I EF.