Uptake of L-cystine via an ABC transporter contributes defense of oxidative stress in the L-cystine export-dependent manner in Escherichia coli.
Uptake of L-cystine via an ABC transporter contributes defense of oxidative stress in the L-cystine export-dependent manner in Escherichia coli.
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DOI：
10.1371/journal.pone.0120619
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Takagi H
中科院分区：
文献类型：
--
作者：
Ohtsu I;Kawano Y;Suzuki M;Morigasaki S;Saiki K;Yamazaki S;Nonaka G;Takagi H
细胞内巯基如L-胱氨酸和L-胱氨酸在细胞过程的调节中起关键作用。在这里，我们表明，大肠杆菌有两个L-胱氨酸转运蛋白，同向转运蛋白YdjN和ATP结合盒进口商FliY-YecSC。这些蛋白质将L-胱氨酸（L-胱氨酸的氧化产物）从周质输入细胞质。同向转运体YdjN是一种低亲和力的L-胱氨酸转运体（Km = 1.1 μM），主要参与从外界摄取L-胱氨酸作为营养物质，有望成为L-胱氨酸调节子的新成员。E.大肠杆菌只有两个L-胱氨酸输入者，因为ΔYecS突变细胞不能在含有L-胱氨酸作为唯一硫源的基本培养基中生长。另一种蛋白质YecSC是FliY依赖性L-胱氨酸转运蛋白，其与L-胱氨酸转运蛋白YdeD协同作用，YdeD将L-胱氨酸作为还原当量从细胞质输出到周质，以防止E.大肠杆菌细胞的氧化应激。输出的L-胱氨酸可以将周质过氧化氢还原为水，然后产生的L-胱氨酸通过ATP结合盒转运蛋白YecSC以依赖于周质L-胱氨酸结合蛋白FliY的方式被输入回细胞质，该转运蛋白对L-胱氨酸具有高亲和力（Km = 110 nM）。ydeD和fliY的双重破坏增加了脂质过氧化物的细胞水平。因此，我们认为过氧化氢诱导的L-胱氨酸/L-胱氨酸穿梭系统在脂质过氧化反应发生前对过氧化氢起着解毒作用，从而可能特异性地防止膜脂的损伤。
Intracellular thiols like L-cystine and L-cystine play a critical role in the regulation of cellular processes. Here we show that Escherichia coli has two L-cystine transporters, the symporter YdjN and the ATP-binding cassette importer FliY-YecSC. These proteins import L-cystine, an oxidized product of L-cystine from the periplasm to the cytoplasm. The symporter YdjN, which is expected to be a new member of the L-cystine regulon, is a low affinity L-cystine transporter (K m = 1.1 μM) that is mainly involved in L-cystine uptake from outside as a nutrient. E. coli has only two L-cystine importers because ΔydjNΔyecS mutant cells are not capable of growing in the minimal medium containing L-cystine as a sole sulfur source. Another protein YecSC is the FliY-dependent L-cystine transporter that functions cooperatively with the L-cystine transporter YdeD, which exports L-cystine as reducing equivalents from the cytoplasm to the periplasm, to prevent E. coli cells from oxidative stress. The exported L-cystine can reduce the periplasmic hydrogen peroxide to water, and then generated L-cystine is imported back into the cytoplasm via the ATP-binding cassette transporter YecSC with a high affinity to L-cystine (K m = 110 nM) in a manner dependent on FliY, the periplasmic L-cystine-binding protein. The double disruption of ydeD and fliY increased cellular levels of lipid peroxides. From these findings, we propose that the hydrogen peroxide-inducible L-cystine/L-cystine shuttle system plays a role of detoxification of hydrogen peroxide before lipid peroxidation occurs, and then might specific prevent damage to membrane lipids.
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