A bacterial glutathione transporter (Escherichia coli CydDC) exports reductant to the periplasm
A bacterial glutathione transporter (Escherichia coli CydDC) exports reductant to the periplasm
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DOI：
10.1074/jbc.m503075200
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发表时间：
2005-09-16
影响因子：
4.8
通讯作者：
Poole, RK
中科院分区：
文献类型：
--
作者：
Pittman, MS;Robinson, HC;Poole, RK
谷胱甘肽（GSH）是一种主要的生物抗氧化剂，在原核生物和真核细胞中维持氧化还原平衡，并与具有药理学和农学重要性的化合物形成可输出的缀合物。然而，在原核生物中没有GSH转运蛋白的特征。我们在这里表明，异源二聚体ATP结合盒型转运蛋白，CydDC，介导GSH跨大肠杆菌细胞质膜的运输。在外翻的膜囊泡中，GSH通过ATP驱动的、质子载体不敏感的、原钒酸盐敏感的机制进口，相当于在完整细胞中出口到周质。GSH转运和细胞色素bd醌醇氧化酶组装在cydD 1突变体中被废除。葡萄糖二硫化物（GSSG）在Cyd（+）或Cyd（-）菌株中均不转运。外源GSH恢复缺陷的群集运动和青霉素敏感性cydD突变体和青霉素敏感性gshA突变体缺陷的GSH合成。在二硫键形成缺陷的dsbD突变体中cydDC操纵子的过表达恢复了二硫苏糖醇耐受性和周质细胞色素B组装，揭示了还原剂输出到周质的冗余途径。这些结果确定了第一个原核谷胱甘肽转运蛋白，并表明谷胱甘肽在周质氧化还原稳态的关键作用。
Glutathione (GSH), a major biological antioxidant, maintains redox balance in prokaryotes and eukaryotic cells and forms exportable conjugates with compounds of pharmacological and agronomic importance. However, no GSH transporter has been characterized in a prokaryote. We show here that a heterodimeric ATP-binding cassette-type transporter, CydDC, mediates GSH transport across the Escherichia coli cytoplasmic membrane. In everted membrane vesicles, GSH is imported via an ATP-driven, protonophore-insensitive, orthovanadate-sensitive mechanism, equating with export to the periplasm in intact cells. GSH transport and cytochrome bd quinol oxidase assembly are abolished in the cydD1 mutant. Glutathione disulfide ( GSSG) was not transported in either Cyd(+) or Cyd(-) strains. Exogenous GSH restores defective swarming motility and benzylpenicillin sensitivity in a cydD mutant and also benzylpenicillin sensitivity in a gshA mutant defective in GSH synthesis. Overexpression of the cydDC operon in dsbD mutants defective in disulfide bond formation restores dithiothreitol tolerance and periplasmic cytochrome b assembly, revealing redundant pathways for reductant export to the periplasm. These results identify the first prokaryotic GSH transporter and indicate a key role for GSH in periplasmic redox homeostasis.