In vivo evidence for the iron-binding activity of an iron-sulfur cluster assembly protein IscA in Escherichia coli.
In vivo evidence for the iron-binding activity of an iron-sulfur cluster assembly protein IscA in Escherichia coli.
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DOI：
10.1042/bj20101507
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发表时间：
2010-12-15
期刊：
影响因子：
--
通讯作者：
Ding H
中科院分区：
文献类型：
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作者：
Wang W;Huang H;Tan G;Si F;Liu M;Landry AP;Lu J;Ding H
IscA是原核生物和真核生物中铁硫簇组装机制的关键成员，然而，IscA的生理功能仍然是难以捉摸的。在这里，我们报告的体内证据表明，在大肠杆菌细胞中的IscA的铁结合活性。在M9基本培养基中添加外源铁（1 μ M）足以使在E.在需氧生长条件下培养大肠杆菌细胞。相比之下，IscU，一种铁硫簇组装支架蛋白，或CyaY，一种细菌共济失调蛋白同源物，不能结合E.大肠杆菌细胞在相同的实验条件下。有趣的是，IscA的强铁结合活性在E.大肠杆菌细胞在厌氧生长条件下。另外的研究表明，培养基中的氧促进IscA中的铁结合，并且IscA中的铁结合反过来防止在有氧条件下形成生物学上不可接近的氢氧化铁。与IscA在好氧和厌氧条件下的铁结合活性差异一致，我们发现IscA和它的副产物SufA在大肠杆菌中的铁硫簇组装中是必不可少的。大肠杆菌细胞在需氧生长条件下生长，但在厌氧生长条件下不生长。这些结果为IscA可能作为铁分子伴侣参与E.大肠杆菌细胞培养。
IscA is a key member of the iron-sulfur cluster assembly machinery in prokaryotic and eukaryotic organisms; however, the physiological function of IscA still remains elusive. Here we report the in vivo evidence demonstrating the iron binding activity of IscA in Escherichia coli cells. Supplement of exogenous iron (1μM) in the M9 minimal medium is sufficient to maximize the iron binding in IscA expressed in E. coli cells under aerobic growth conditions. In contrast, IscU, an iron-sulfur cluster assembly scaffold protein, or CyaY, a bacterial frataxin homologue, fails to bind any iron in E. coli cells under the same experimental conditions. Interestingly, the strong iron binding activity of IscA is greatly diminished in E. coli cells under anaerobic growth conditions. Additional studies reveal that oxygen in medium promotes the iron binding in IscA and that the iron binding in IscA in turn prevents formation of biologically inaccessible ferric hydroxide under aerobic conditions. Consistent with the differential iron binding activity of IscA under aerobic and anaerobic conditions, we find that IscA and its paralog SufA are essential for the iron-sulfur cluster assembly in E. coli cells under aerobic growth conditions but not under anaerobic growth conditions. The results provide the in vivo evidence that IscA may act as an iron chaperone for the biogenesis of iron-sulfur clusters in E. coli cells under aerobic conditions.