Sre1, an iron-modulated GATA DNA-binding protein of iron-uptake genes in the fungal pathogen Histoplasma capsulatum
Sre1, an iron-modulated GATA DNA-binding protein of iron-uptake genes in the fungal pathogen Histoplasma capsulatum
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DOI：
10.1021/bi800066s
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发表时间：
2008-07-08
期刊：
影响因子：
2.9
通讯作者：
Rine, Jasper
中科院分区：
文献类型：
--
作者：
Chao, Lily Y.;Marletta, Michael A.;Rine, Jasper
致病性真菌荚膜组织浆体在巨噬细胞感染期间需要铁才能存活。由于铁在高水平时是有毒的，包括荚膜孢子虫在内的致病性生物的铁获取是一个高度调控的过程。在对过量铁的反应中，荚膜荚膜荚膜菌抑制参与铁摄取的基因转录。我们在这里报道了编码gata型蛋白的基因SRE1与参与铁载体生物合成的基因启动子序列结合。Sre1与真菌铁载体生物合成负调控因子序列相似。在缺铁条件下，SRE1的表达减少，强调了其作为参与铁摄取基因的负调节因子的作用。Sre1p特异性结合含有5‘-(G/A)ATC(T/A)GATAA-3’序列的DNA，并且这种结合是铁和锌依赖的。金属分析表明，亚化学计量量的铁，主要是Fe3+，结合到纯化的蛋白质。每个单体大约需要0.5-1等量的Fe3+才能达到完全的dna结合活性。富含半胱氨酸区域的保守半胱氨酸残基突变导致结合铁减少。铁的缺失导致dna结合亲和力降低2.5倍，表明铁直接参与SRE1对铁摄取基因的调控。
The pathogenic fungus Histoplasma capsulatum requires iron for its survival during macrophage infection. Because iron is toxic at high levels, iron acquisition in pathogenic organisms, including H. capsulatum, is a highly regulated process. In response to excess iron, H. capsulatum represses transcription of genes involved in iron uptake. We report here that SRE1, a gene encoding a GATA-type protein, bound to promoter sequences of genes involved in siderophore biosynthesis. Sre1 had sequence similarity to the fungal negative regulators of siderophore biosynthesis. Expression of SRE1 was reduced under iron-starving conditions, underscoring its role as a negative regulator of genes involved in iron uptake. Sre1p specifically bound DNA containing the 5'-(G/A)ATC(T/A)GATAA-3' sequence, and that binding was both iron- and zinc-dependent. Metal analysis indicated that a substoichiometric amount of iron, predominately Fe3+, was bound to the purified protein. About 0.5-1 equiv of Fe3+ per monomer was necessary for full DNA-binding activity. Mutations in the conserved cysteine residues in the cysteine-rich region led to a decrease in bound iron. The loss of iron led to a similar to 2.5-fold decrease in DNA-binding affinity, indicating that iron was directly involved in SRE1 regulation of iron-uptake genes.