New insights on vanadium binding to human serum transferrin

The knowledge on the binding of vanadium ions and complexes to serum proteins and how vanadium might be transported in blood and up-taken by cells has received much attention during the last decade, particularly as far as the transport of (VO2+)-O-IV is concerned. In this work we revise and discuss some relevant aspects of previous research, namely the two main types of binding proposed for transport of (VO)-O-IV(carrier)(2) complexes. New results, obtained by circular dichroism (CD), EPR and gel electrophoresis, regarding the binding of vanadium to hTF in the oxidation states +5 and +3 are also presented. Namely, evidences for the binding of V-V-species to diferric-transferrin, designated by (Fe-III)(2)hTF, as well as to (Al-III)(2)hTF, are presented and discussed, the possibility of up-take of vanadate by cells through (Fe-III)(2)hTF endocytosis being suggested. It is also confirmed that V-III binds strongly to hTF, forming di-vanadium(III)-transferrin, designated by (V-III)(2)hTF, and gel electrophoresis experiments indicate that (V-III)(2)hTF corresponds to a 'closed conformation' similar to (FeIII) 2hTF. (C) 2013 Elsevier B.V. All rights reserved.