Oxalate- and Ga3+-induced structural changes in human serum transferrin and its recombinant N-lobe: 1H NMR detection of preferential C-lobe Ga3+ binding

Proton nuclear magnetic resonance spectroscopy was used to study the binding of Ga3+ and the synergistic anion oxalate to human serum transferrin (HTF) and its recombinant N-lobe (HTF/2N). The structural consequences of reverse-order metal loading was also examined. Specific protein resonances displayed a sensitivity to oxalate binding. In addition, results revealed a slow exchange between apo-HTF and Ga-loaded HTF or HTF/2N. Some orientational changes was found among residues in hydrophobic pockets in the interdomain hinge region near the metal binding site following Ga3+ binding.