Mg2+ sensing by the Mg2+ sensor PhoQ of Salmonella enterica
Mg2+ sensing by the Mg2+ sensor PhoQ of Salmonella enterica
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DOI：
10.1016/s0022-2836(02)01268-8
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发表时间：
2003-01-24
影响因子：
5.6
通讯作者：
Groisman, EA
中科院分区：
文献类型：
--
作者：
Chamnongpol, S;Cromie, M;Groisman, EA
PhoP/PhoQ 双组分调控系统控制着几种革兰氏阴性菌对低 Mg2+ 环境的适应和毒力。在低 Mg2+ 条件下生长期间，传感器 PhoQ 会改变响应调节因子 PhoP 的活性，促进基因转录，而在高 Mg2+ 条件下生长则抑制 PhoP 激活基因的转录。 PhoQ 蛋白具有 146 个氨基酸残基的周质结构域，可在体外结合 Mg2+，并且是体内 Mg2+ 介导的抑制所必需的。在这里，我们鉴定了沙门氏菌 PhoQ 蛋白的周质突变体，即使在高 Mg2+ 浓度下也允许 PhoP 激活基因的转录。当在含有由乙酰磷酸磷酸化的 PhoP 变体的菌株中表达时，一些突变体无法在高 Mg2+ 条件下抑制 PhoP 促进的转录，而其他突变体则表现出野生型的能力。允许在高 Mg2+ 中表达 PhoP 激活基因的突变体 PhoQ 蛋白在体外显示出铁介导的裂解模式，该模式与野生型 PhoQ 所显示的模式不同，表明 Mg2+ 结合发生了改变。保守组氨酸残基 (H277) 被丙氨酸取代的 PhoQ 蛋白在低 Mg2+ 条件下不能促进 PhoP 激活基因的转录，但可以在高 Mg2+ 条件下关闭表达。我们的研究表明，野生型对 Mg2+ 的反应需要残基 G93、W97、H120 和 T156，并表明 Mg2+ 与周质结构域的结合调节 PhoQ 蛋白的多种活性。 (C) 2003 Elsevier Science Ltd. 保留所有权利。
The PhoP/PhoQ two-component regulatory system governs the adaptation to low Mg2+ environments and virulence in several Gram-negative species. During growth in low Mg2+, the sensor PhoQ modifies the activity of the response regulator PhoP promoting gene transcription, whereas growth in high Mg2+ represses transcription of PhoP-activated genes. The PhoQ protein harbors a periplasmic domain of 146 amino acid residues that binds Mg2+ in vitro and is required for Mg2+-mediated repression in vivo. Here, we identify periplasmic mutants of the Salmonella PhoQ protein that allow transcription of PhoP-activated genes even under high Mg2+ concentrations. When expressed in a strain harboring a PhoP variant that is phosphorylated from acetyl phosphate, some of the mutants failed to repress PhoP-promoted transcription in high Mg2+, whereas others displayed a wild-type ability to do so. Mutant PhoQ proteins that allowed expression of PhoP-activated genes in high Mg2+ displayed a pattern of iron-mediated cleavage in vitro that was different from that displayed by wild-type PhoQ, indicative of altered Mg2+ binding. A PhoQ protein with the conserved histidine residue (H277) substituted by alanine could not promote transcription of PhoP-activated genes in low Mg2+ but could turn off expression in response to high Mg2+. Our studies demonstrate that residues G93, W97, H120 and T156 are required for a wild-type response to Mg2+, and suggest that Mg2+ binding to the periplasmic domain regulates several activities in the PhoQ protein. (C) 2003 Elsevier Science Ltd. All rights reserved.