Nicotianamine chelates both FeIII and FeII.: Implications for metal transport in plants
Nicotianamine chelates both FeIII and FeII.: Implications for metal transport in plants
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DOI：
10.1104/pp.119.3.1107
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发表时间：
1999-03-01
期刊：
影响因子：
7.4
通讯作者：
Hider, RC
中科院分区：
文献类型：
--
作者：
von Wirén, N;Klair, S;Hider, RC
烟酰胺（NA）存在于所有植物中，并螯合金属阳离子，包括Fe-II，但据报道不螯合Fe-III。然而，NA和各种Fe-III螯合氨基羧酸盐的Fe-II和Zn-II亲和常数的比较表明，NA应该螯合Fe-III。在Fe-III存在下形成的FeNA复合物的高压电泳显示，该复合物的净电荷为0，与Fe-III的六齿螯合一致。对Fe-III的亲和常数的测量得到的值为10（20.6），其大于NA与Fe-II缔合的亲和常数（10（12.8））。然而，毛细管电泳显示，在存在的Fe-II和Fe-III，NA优先螯合Fe-II，表明Fe（II）NA络合物在有氧条件下是动力学稳定的。此外，NA的Fe络合物是相对较差的芬顿试剂，如通过它们介导脱氧核糖的H2 O2依赖性氧化的能力所测量的。这表明NA在清除Fe和保护细胞免受氧化损伤方面具有重要作用。NA和一种典型的植物铁载体2 '-脱氧mugineic酸对金属离子螯合的pH依赖性表明，尽管两者都具有螯合Fe的能力，但当两者都存在时，2'-脱氧mugineic酸在酸性pH值下主导螯合过程，而NA在碱性pH值下主导螯合过程。NA在长距离运输的金属在木质部和韧皮部的作用的后果进行了讨论。
Nicotianamine (NA) occurs in all plants and chelates metal cations, including Fe-II, but reportedly not Fe-III. However, a comparison of the Fe-II and Zn-II affinity constants of NA and various Fe-III chelating aminocarboxylates suggested that NA should chelate Fe-III High-voltage electrophoresis of the FeNA complex formed in the presence of Fe-III showed that the complex had a net charge of 0, consistent with the hexadentate chelation of Fe-III. Measurement of the affinity constant for Fe-III yielded a value of 10(20.6), which is greater than that for the association of NA with Fe-II (10(12.8)). However, capillary electrophoresis showed that in the presence of Fe-II and Fe-III, NA preferentially chelates Fe-II, indicating that the Fe(II)NA 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.