Functional characterization of AtATM1, AtATM2, and AtATM3, a subfamily of Arabidopsis half-molecule ATP-binding cassette transporters implicated in iron homeostasis
Functional characterization of AtATM1, AtATM2, and AtATM3, a subfamily of Arabidopsis half-molecule ATP-binding cassette transporters implicated in iron homeostasis
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DOI：
10.1074/jbc.m702383200
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发表时间：
2007-07-20
影响因子：
4.8
通讯作者：
Rea, Philip A.
中科院分区：
文献类型：
--
作者：
Chen, Sixue;Sánchez-Fernández, Rocío;Rea, Philip A.
描述了拟南芥ATP结合盒转运蛋白的最小亚家族之一AtATM的功能。命名为AtATM 1，AtAATM 2和AtATM 3，这些半分子ABC蛋白与酵母线粒体膜蛋白ATM 1（ScATM 1）同源，这显然与神经合成的铁/硫簇的输出有关。酵母ATM 1缺陷（atm 1）突变体生长非常缓慢（具有娇小的表型），呼吸缺陷，在其线粒体中积累毒性水平的铁，并显示出增强的补偿性高亲和力铁摄取。在拟南芥的三个ATM中，AtATM 3与ScATM 1的功能最相似。异源表达的AtATM 3不仅能够补充酵母atm 1娇小表型，而且还能够抑制与ScATM 1染色体拷贝丢失相关的组成性高亲和力铁摄取能力，消除线粒体内铁过度积累，并恢复线粒体呼吸功能和细胞色素c水平。相比之下，AtATM 1仅弱抑制atm 1表型，AtATM 2在该系统中表达时几乎不发挥抑制作用，而是具有毒性。AtATM 3和AtATM 1之间的差异在交换其靶肽后得以保持，并且当在酵母中表达为GFP融合体时，这些蛋白质以及AtATM 2与线粒体荧光MitoTracker Red共定位。虽然它的毒性时异源表达在酵母中，除了与GFP融合时，排除了天然AtATM 2的功能分析，一个共同的功能，线粒体出口的Fe/S簇或其前体的细胞溶质Fe/S蛋白的组装，推断为AtATM 3和AtATM 1。
The functional capabilities of one of the smallest subfamilies of ATP-binding cassette transporters from Arabidopsis thaliana, the AtATMs, are described. Designated AtATM1, AtAATM2, and AtATM3, these half-molecule ABC proteins are homologous to the yeast mitochondrial membrane protein ATM1 (ScATM1), which is clearly implicated in the export of mitochondrially synthesized iron/sulfur clusters. Yeast ATM1-deficient (atm1) mutants grow very slowly (have a petite phenotype), are respiration-deficient, accumulate toxic levels of iron in their mitochondria, and show enhanced compensatory high affinity iron uptake. Of the three Arabidopsis ATMs, AtATM3 bears the closest functional resemblance to ScATM1. Heterologously expressed AtATM3 is not only able to complement the yeast atm1 petite phenotype but is also able to suppress the constitutively high capacity for high affinity iron uptake associated with loss of the chromosomal copy of ScATM1, abrogate intra-mitochondrial iron hyperaccumulation, and restore mitochondrial respiratory function and cytochrome c levels. By comparison, AtATM1 only weakly suppresses the atm1 phenotype, and AtATM2 exerts little or no suppressive action but instead is toxic when expressed in this system. The differences between AtATM3 and AtATM1 are maintained after exchanging their target peptides, and these proteins as well as AtATM2 colocalize with the mitochondrial fluor MitoTracker Red when expressed in yeast as GFP fusions. Although its toxicity when heterologously expressed in yeast, except when fused with GFP, precludes the functional analysis of native AtATM2, a common function, mitochondrial export of Fe/S clusters or their precursors for the assembly of cytosolic Fe/S proteins, is inferred for AtATM3 and AtATM1.