SPECTROSCOPIC STUDIES OF THE INTERACTION OF ALUMINUM(III) WITH TRANSFERRINS

In this review, we summarize the spectroscopic techniques used to exam ine the binding of aluminum to the transferrins, a class of vertebrate iron-binding proteins. Interest in the binding of Al3+ by the transfe rrins, in particular serum transferrin, stems from the suggested role of metal detoxification in plasma by this protein and the association of this metal ion in human disorders such as Alzheimer's disease. A nu mber of indirect methods of observing the binding of Al3+ to the trans ferrins, such as UV-visible spectroscopy, X-ray solution scattering, a nd H-1 and C-13 nuclear magnetic resonance(NMR) spectroscopy, have rev ealed information on the coordination and structure of the metal ion b inding sites as well as conformational changes that occur on the bindi ng of metal ions. Various NMR approaches, including Al-27 NMR, have el ucidated subtle differences within the binding sites and between sever al transferrins. Most notably, the recent detection of transferrin-bou nd Al-27 NMR signals, characteristic of quadrupolar relaxation in the limit of slow molecular motion, has allowed us to observe directly the metal ion bound to the protein.