Ferric uptake regulator (Fur) reversibly binds a [2Fe-2S] cluster to sense intracellular iron homeostasis in Escherichia coli
Ferric uptake regulator (Fur) reversibly binds a [2Fe-2S] cluster to sense intracellular iron homeostasis in Escherichia coli
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DOI：
10.1074/jbc.ra120.014814
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发表时间：
2020-11-13
影响因子：
4.8
通讯作者：
Ding, Huangen
中科院分区：
文献类型：
--
作者：
Fontenot, Chelsey R.;Tasnim, Homyra;Ding, Huangen
铁摄取调节因子（Fur）是一种调节细菌细胞内铁稳态的全局性转录因子。目前的假说指出，当细胞内的“游离”铁浓度升高时，毛皮结合亚铁，铁结合的毛皮抑制编码铁摄取系统的基因，并刺激编码铁储存蛋白的基因。然而，“铁结合”的毛皮从未从任何细菌中分离出来。在这里，我们报告说，大肠杆菌毛皮有一个明亮的红色时，表达在E。大肠杆菌突变体细胞含有升高的细胞内游离铁含量，因为删除铁硫簇组装蛋白IscA和SufA。结合EPR和穆斯堡尔谱测量和定点诱变研究的酸不稳定的铁和硫化物含量分析表明，红色毛皮蛋白结合的[2Fe-2S]集群通过保守的半胱氨酸残基。Fur蛋白中[2Fe-2S]簇的占有率与E. coliiscA/sufA突变体细胞中的表达量下降到约4%。大肠杆菌细胞。用膜渗透性铁螯合剂2，2 '-联吡啶去除胞内游离铁，能有效地去除大肠杆菌Fur中的[2Fe-2S]簇。表明Fur通过与[2Fe-2S]簇的可逆结合来感知细胞内游离铁含量。Fur中[2Fe-2S]簇的结合似乎是高度保守的，因为来自流感嗜血杆菌的Fur同系物在E.大肠杆菌细胞还可逆地结合[2Fe-2S]簇以感知细胞内铁稳态。
The ferric uptake regulator (Fur) is a global transcription factor that regulates intracellular iron homeostasis in bacteria. The current hypothesis states that when the intracellular "free" iron concentration is elevated, Fur binds ferrous iron, and the iron-bound Fur represses the genes encoding for iron uptake systems and stimulates the genes encoding for iron storage proteins. However, the "iron-bound" Fur has never been isolated from any bacteria. Here we report that the Escherichia coli Fur has a bright red color when expressed in E. coli mutant cells containing an elevated intracellular free iron content because of deletion of the iron-sulfur cluster assembly proteins IscA and SufA. The acid-labile iron and sulfide content analyses in conjunction with the EPR and Mossbauer spectroscopy measurements and the site-directed mutagenesis studies show that the red Fur protein binds a [2Fe-2S] cluster via conserved cysteine residues. The occupancy of the [2Fe-2S] cluster in Fur protein is similar to 31% in the E. coli iscA/sufA mutant cells and is decreased to similar to 4% in WT E. coli cells. Depletion of the intracellular free iron content using the membrane-permeable iron chelator 2,2 '-dipyridyl effectively removes the [2Fe-2S] cluster from Fur in E. coli cells, suggesting that Fur senses the intracellular free iron content via reversible binding of a [2Fe-2S] cluster. The binding of the [2Fe-2S] cluster in Fur appears to be highly conserved, because the Fur homolog from Hemophilus influenzae expressed in E. coli cells also reversibly binds a [2Fe-2S] cluster to sense intracellular iron homeostasis.