Mg2+ homeostasis and avoidance of metal toxicity
Mg2+ homeostasis and avoidance of metal toxicity
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DOI：
10.1046/j.1365-2958.2002.02917.x
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发表时间：
2002-04-01
影响因子：
3.6
通讯作者：
Groisman, EA
中科院分区：
文献类型：
--
作者：
Chamnongpol, S;Groisman, EA
由于多种细胞功能都需要 Mg2+，因此必须严格调节其细胞内水平。在革兰氏阴性细菌肠沙门氏菌中，三种转运蛋白介导 Mg2+ 摄取：P 型 ATP 酶 MgtA 和 MgtB，其表达在低 Mg2+ 条件下由 Mg2+ 调节的 PhoP/PhoQ 双组分系统转录诱导。 CorA，其转录既不受 Mg2+ 水平的调节，也不受 PhoP/PhoQ 系统的调节。我们现在报道 phoP 或 mgtA 和 mgtB 缺陷的突变体对氧化应激依赖性 Fe (II) 介导的杀伤高度敏感。这些突变体表现出铁积累增加和 Ni2+ 吸收增加。 corA 基因失活恢复了对 phoP 突变体的 Fe(II) 抗性并消除了 Ni2+ 的吸收。 phoP 突变体中 corA 转录和 CorA 蛋白水平均未改变，这表明 CorA 响应 PhoP 调节决定簇的存在而改变其活性。在低 Mg2+ 环境中下调 CorA 活性可能使沙门氏菌能够避免有毒金属不受控制的流入。
Because Mg2+ is required for a wide variety of cellular functions, its intracellular levels must be tightly regulated. In the Gram-negative bacterium Salmonella enterica , three transporters mediate Mg2+ uptake: the P-type ATPases MgtA and MgtB, whose expression is transcriptionally induced in low Mg2+ by the Mg2+ -regulated PhoP/PhoQ two-component system; and CorA, whose transcription is regulated neither by the levels of Mg2+ nor by the PhoP/PhoQ system. We now report that mutants defective in phoP or in both mgtA and mgtB are hypersensitive to oxidative stress-dependent Fe (II)-mediated killing. These mutants display increased iron accumulation and heightened Ni2+ uptake. Inactivation of the corA gene restored Fe(II) resistance to the phoP mutant and eliminated uptake of Ni2+ . Neither corA transcription nor CorA protein levels were altered in the phoP mutant, suggesting that CorA alters its activity in response to the presence of PhoP-regulated determinants. Downregulation of CorA activity in low Mg2+ environments may enable Salmonella to avoid the uncontrolled influx of toxic metals.