The Essential Cytosolic Iron-Sulfur Protein Nbp35 Acts without Cfd1 Partner in the Green Lineage
The Essential Cytosolic Iron-Sulfur Protein Nbp35 Acts without Cfd1 Partner in the Green Lineage
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DOI：
10.1074/jbc.m807303200
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发表时间：
2008-12-19
影响因子：
4.8
通讯作者：
Balk, Janneke
中科院分区：
文献类型：
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作者：
Bych, Katrine;Netz, Daili J. A.;Balk, Janneke
在光合真核生物中，铁硫（Fe-S）辅因子的组装组分已在质体和线粒体中进行了研究，但胞质和核Fe-S簇蛋白如何组装尚不清楚。我们已经表征了与酵母和哺乳动物的Nbp 35具有序列相似性的植物P环NTR，其是胞质Cfd 1-Nbp 35复合物介导的Fe-S簇组装的蛋白质。基因组分析显示，NBP 35在绿色谱系中是保守的，但CFD 1不存在。此外，植物和藻类NBP 35蛋白在C末端缺乏特征性的CXXC基序，这被认为是Fe-S簇结合所需的。然而，化学重建和光谱分析表明，拟南芥（At）NBP 35结合的[4Fe-4S]簇在C端以及稳定的[4Fe-4S]簇在N端。Holo-AtNBP 35能够在体外将Fe-S簇转移到脱辅基蛋白上。当在酵母中表达时，AtNBP 35依赖于半胱氨酸脱硫酶Nfs 1结合Fe-55，并且能够部分拯救cfd 1突变体的生长，但不能拯救nbp 35突变体的生长。AtNBP 35基因在植物中组成型表达，其破坏与胚胎发育的停滞有关。这些结果表明，尽管与酵母Cfd 1-Nbp 35 Fe-S支架复合物存在相当大的差异，但AtNBP 35保留了类似的Fe-S簇结合和转移特性，并发挥了重要的功能。
In photosynthetic eukaryotes assembly components of iron-sulfur (Fe-S) cofactors have been studied in plastids and mitochondria, but how cytosolic and nuclear Fe-S cluster proteins are assembled is not known. We have characterized a plant P loop NTPase with sequence similarity to Nbp35 of yeast and mammals, a protein of the cytosolic Cfd1-Nbp35 complex mediating Fe-S cluster assembly. Genome analysis revealed that NBP35 is conserved in the green lineage but that CFD1 is absent. Moreover, plant and algal NBP35 proteins lack the characteristic CXXC motif in the C terminus, thought to be required for Fe-S cluster binding. Nevertheless, chemical reconstitution and spectroscopy showed that Arabidopsis (At) NBP35 bound a [4Fe-4S] cluster in the C terminus as well as a stable [4Fe-4S] cluster in the N terminus. Holo-AtNBP35 was able to transfer an Fe-S cluster to an apoprotein in vitro. When expressed in yeast, AtNBP35 bound Fe-55 dependent on the cysteine desulfurase Nfs1 and was able to partially rescue the growth of a cfd1 mutant but not of an nbp35 mutant. The AtNBP35 gene is constitutively expressed in planta, and its disruption was associated with an arrest of embryo development. These results show that despite considerable divergence from the yeast Cfd1-Nbp35 Fe-S scaffold complex, AtNBP35 has retained similar Fe-S cluster binding and transfer properties and performs an essential function.