Transferrin, the major iron transport protein in the blood, apparently also transports trivalent chromium in vivo via endocytosis. Recent in vitro studies have, however, suggested that the release of chromic ions from serum transferrin is too slow to be biologically relevant. Consequently, the release of chromium(III) from human serum transferrin has been examined under conditions mimicking an endosome during endocytosis. At pH 4.5 and 5.5, the release of Cr(III) from transferrin occurs rapidly from the C-lobe binding site. While appreciably slower, the release of Cr(III) from the N-lobe binding site in the presence biological chelating agents is potentially sufficiently fast to be physiologically relevant. When Cr(III)-loaded transferrin is added to soluble transferrin receptor, the loss of Cr(III) from both binding sites becomes rapid at acidic pH, making Cr loss sufficiently rapid to be physiologically relevant. The preparation of Cr2-Tf before acidification also affects the rate of Cr(III) loss after acidification, as well EPR signal of the N-lobe Cr(III) site, which may have implications on conformation of Tf in the release of Cr(III). However, detailed studies of conformation changes of transferrin associated with the binding and release of chromium along with investigations of how and at what rate Cr(III) is transported from the endosome will be required before this question of whether transferrin transport Cr(III) in vivo can be definitively resolved.

Release of Cr(III) from transferrin: Conformation effects and viability of potential endosomal chelators

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.