Iron transport by Nramp2/DMT1:: pH regulation of transport by 2 histidines in transmembrane domain 6
Iron transport by Nramp2/DMT1:: pH regulation of transport by 2 histidines in transmembrane domain 6
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DOI：
10.1182/blood-2002-07-2108
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发表时间：
2003-05-01
期刊：
影响因子：
20.3
通讯作者：
Gros, P
中科院分区：
文献类型：
--
作者：
Lam-Yuk-Tseung, S;Govoni, G;Gros, P
天然耐药相关巨噬细胞蛋白1（Nramp 1）突变会损害吞噬细胞功能并导致感染易感性，而Nramp 2（二价金属转运蛋白1 [DMT 1]）突变会影响铁稳态并导致严重的小细胞性贫血。通过诱变研究了Nramp超家族的结构-功能关系，然后在酵母和哺乳动物细胞中进行功能表征。这些研究确定了跨膜结构域（TM）1、4和7中3个带负电荷且高度保守的残基为必需残基。Nramp 2/DMT 1的阳离子转运。在天然存在的小细胞性贫血小鼠（小鼠）和贝尔格莱德（大鼠）突变体中发现的TM 4中引入带电残基（Gly 185 Arg），分别导致哺乳动物和酵母细胞的部分或完全功能丧失。在TM 6中鉴定出一对突变敏感且高度保守的组氨酸（His 267，His 272）。令人惊讶的是，可以通过降低转运测定的pH来拯救失活的His 267和His 272突变体。这表明His 267/His 272不直接参与金属结合，而是在Nramp蛋白的金属转运的pH调节中发挥重要作用。(C)2003年，美国血液学会。
Mutations at natural resistance-associated macrophage protein 1 (Nramp1) impair phagocyte function and cause susceptibility to infections while mutations at Nramp2 (divalent metal transporter 1 [DMT1]) affect iron homeostasis and cause severe microcytic anemia. Structure-function relationships in the Nramp superfamily were studied by mutagenesis, followed by functional characterization in yeast and in mammalian cells. These studies identify 3 negatively charged and highly conserved residues in transmembrane domains (TM) 1, 4, and 7 as essential. for cation transport by Nramp2/DMT1. The introduction of a charged residue (Gly185Arg) in TM4 found in the naturally occurring microcytic anemia mk (mouse) and Belgrade (rat) mutants is shown to cause a partial or complete loss of function in mammalian and yeast cells, respectively. A pair of mutation-sensitive and highly conserved histidines (His267, His272) was identified in TM6. Surprisingly, inactive His267 and His272 mutants could be rescued by lowering the pH of the transport assay. This indicates that His267/His272 are not directly involved in metal binding but, rather, play an important role in pH regulation of metal transport by Nramp proteins. (C) 2003 by The American Society of Hematology.