Transplasma Membrane Electron Transport Functions as a Ferric Reductase
We have previously presented evidence that ferric ions and iron in diferric transferric can be reduced at the cell surface by the transplasma membrane electron transport system acting in conjuction with the transferrin receptor 1,2. In this paper we examine the reaction further especially in relation to the inhibition of both ferric citrate and diferric transferrin reduction by apotransferrin. We also consider the difference in activity found with different diferric transferrin preparations containing different amounts of loosely bound ferric iron. We will also consider the effects of argon, and cell transformation on the rate of ferric iron reduction in the presence and absence of diferric transferrin. The objective is to evaluate the extent to which loosely bound iron on transferrin can contribute to the formation of ferrous bathophenanthroline disulfonate (Fe(BPS)3) through the transmembrane electron transport system. We also show that iron reduction at acidic pH by the transmembrane enzyme is not inhibited by apotransferrin which would favor its role for ferric reduction in acidic endosomes.
KeywordsFerric Citrate Ferric Ammonium Ammonium Citrate Ferric Ammonium Citrate Ll210 Cell
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- 1.H. Löw, C. Grebing, A. Lindgren, M. Tally, I.L. Sun and F.L. Crane. Involment of transferrin in the reduction of iron by the transplasma membrane electron transport system, J. Bioenerg. Biomemb. 19, 535–549 (1987).Google Scholar
- 2.I.L. Sun, P. Navas, F.L. Crane, D.J. Morré and H. Löw. NADH diferric transferrin reductase in liver plasma membrane, J. Biol. Chem. 262, 15915–15921 (1987).Google Scholar
- 10.W. Toole-Simms. PhD Thesis Purdue University 1988 pp.Google Scholar