Nicotianamine Chelates Both FeIII and FeII. Implications for Metal Transport in Plants1

DOI PDF 35 Citations
  • Nicolaus von Wirén
    Department of Pharmacy, King's College London, Manresa Road, London SW3 6LX, United Kingdom (N.v.W., S.K., S.B., H.K., R.C.H.)
  • Sukhbinder Klair
    Department of Pharmacy, King's College London, Manresa Road, London SW3 6LX, United Kingdom (N.v.W., S.K., S.B., H.K., R.C.H.)
  • Suhkibar Bansal
    Department of Pharmacy, King's College London, Manresa Road, London SW3 6LX, United Kingdom (N.v.W., S.K., S.B., H.K., R.C.H.)
  • Jean-Francois Briat
    Laboratoire de Biochimie et Physiologie Moléculaire des Plantes, Institut National de la Recherche Agronomique, Place Viala, F-34060 Montpellier, France (J.-F.B.)
  • Hicham Khodr
    Department of Pharmacy, King's College London, Manresa Road, London SW3 6LX, United Kingdom (N.v.W., S.K., S.B., H.K., R.C.H.)
  • Takayuki Shioiri
    Faculty of Pharmaceutical Sciences, Nagoya City University, Tanabe-dori, Mizuho-ku, Nagoya 467, Japan (T.S.)
  • Roger A. Leigh
    Biochemistry and Physiology Department, IACR-Rothamsted, Harpenden, Hertfordshire AL5 2JQ, United Kingdom (R.A.L.)
  • Robert C. Hider
    Department of Pharmacy, King's College London, Manresa Road, London SW3 6LX, United Kingdom (N.v.W., S.K., S.B., H.K., R.C.H.)

Abstract

<jats:title>Abstract</jats:title> <jats:p>Nicotianamine (NA) occurs in all plants and chelates metal cations, including FeII, but reportedly not FeIII. However, a comparison of the FeII and ZnII affinity constants of NA and various FeIII-chelating aminocarboxylates suggested that NA should chelate FeIII. High-voltage electrophoresis of the FeNA complex formed in the presence of FeIII showed that the complex had a net charge of 0, consistent with the hexadentate chelation of FeIII. Measurement of the affinity constant for FeIII yielded a value of 1020.6, which is greater than that for the association of NA with FeII (1012.8). However, capillary electrophoresis showed that in the presence of FeII and FeIII, NA preferentially chelates FeII, indicating that the FeIINA complex is kinetically stable under aerobic conditions. Furthermore, Fe complexes of NA are relatively poor Fenton reagents, as measured by their ability to mediate H2O2-dependent oxidation of deoxyribose. This suggests that NA will have an important role in scavenging Fe and protecting the cell from oxidative damage. The pH dependence of metal ion chelation by NA and a typical phytosiderophore, 2′-deoxymugineic acid, indicated that although both have the ability to chelate Fe, when both are present, 2′-deoxymugineic acid dominates the chelation process at acidic pH values, whereas NA dominates at alkaline pH values. The consequences for the role of NA in the long-distance transport of metals in the xylem and phloem are discussed.</jats:p>

Journal

  • Plant Physiology

    Plant Physiology 119 (3), 1107-1114, 1999-03-01

    Oxford University Press (OUP)

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