Investigations into the Binding of Iron by Transferrin

Abstract

Evidence from ultraviolet spectral analyses and diffusion experiments has been presented to show that there are a number of loose binding sites on the transferrin molecule which can accommodate up to some one hundred atoms of iron per molecule of transferrin. Spectral evidence indicates that these sites are associated with the ring structure of the molecule’s aromatic aminoacids, and a theoretical explanation for this is presented. Time, temperature and pH have no major influence on such binding, which is rapidly accomplished. The discordant results evident in the literature may well have been due to the unsuspected presence of iron, or other substances, in the loose binding sites. Where the concentration of iron in relation to transferrin has been shown to be greater than two atoms per molecule as in certain blood, urine and cerebrospinal fluid findings, the relative amounts fall within the range that may be explained by loose bindings. Certain substances other than iron can be accommodated in these sites, thus theoretically providing a direct transport system to the bone marrow where the known depressive effects of some of these substances occur. These findings are used to indicate a new method for the estimation of transferrin, a more complete investigation of the relationship of transferrin and iron in serum, and an explanation for the diversity of clinical findings in particular disorders of iron metabolism.