The effect of salt concentration on the iron-binding properties of human transferrin

The salt dependence of the iron-binding properties of transferrin was studied by urea/polyacrylamide-gel electrophoresis. The distribution of iron between the N-terminal and C-terminal binding sites under equilibrium conditions and the rates of release of iron from the two sites were studied. It was found that salt increases the thermodynamic stability of iron binding in the N-terminal site relative to the C-terminal site. Similar behaviour is observed for the kinetics of iron release, where salt retards the rate of removal of iron from the N-terminal site but facilitates removal from the C-terminal site.