Transport of magnesium by a bacterial Nramp-related gene.
Transport of magnesium by a bacterial Nramp-related gene.
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DOI：
10.1371/journal.pgen.1004429
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发表时间：
2014-06
期刊：
影响因子：
4.5
通讯作者：
Winkler WC
中科院分区：
文献类型：
--
作者：
Shin JH;Wakeman CA;Goodson JR;Rodionov DA;Freedman BG;Senger RS;Winkler WC
镁是一种重要的二价金属，具有多种细胞功能。虽然大多数二价阳离子保持在相对较低的细胞内浓度，但镁保持在较高的水平(∼0.5mM-2.0mM)。在此之前，有三个转运蛋白家族被确定为镁的进口：CORA、MGTA/MGTA。在目前的研究中，我们发现，表达与这些转运蛋白无关的细菌蛋白可以完全恢复缺乏已知镁转运蛋白的细菌突变体的生长，这表明它是一个新的镁进口体。我们证明，这种转运活动可能是特异的，而不是底物混杂造成的，因为这些蛋白质不能进口锰。这种镁转运蛋白与Nramp家族蛋白有较远的亲缘关系，Nramp家族已被证明可以运输二价阳离子，但从未被证明识别镁。我们还发现新的镁转运蛋白的基因表达受镁敏感核糖开关的控制。重要的是，我们发现了更多由核糖开关调节的同系物的例子，这表明它们在细菌中经常出现。因此，我们的汇总数据发现了镁进口的一条新的、可能是广泛重要的途径，并强调了核糖开关RNA的鉴定如何有助于揭示其下游基因的新功能，有时甚至是意想不到的功能。镁离子是生命所必需的，相应地，所有生物体都必须编码以供蛋白质运输它们。以前已经确定了三类细菌蛋白(CORA、MGTA/B和MGTA/B)用于离子的运输。这项研究介绍了一种新的镁输入途径，而且，它出人意料地由与天然耐药相关巨噬细胞蛋白(Nramp)远相关的蛋白质提供。Nramp金属转运蛋白广泛存在于生命的三个领域；然而，大多数被认为是作为过渡金属的转运蛋白，如锰或铁。之前表征的Nramps都没有被证明可以运输镁。在这项研究中，我们证明了某些细菌蛋白，与Nramp同源物远亲，表现出镁的运输。我们还发现，这些新的镁转运蛋白受镁敏感调控元件的遗传控制。重要的是，我们发现了许多类似基因共享这种调控安排的额外例子，这表明这些基因可能在细菌中频繁出现，并可能代表一类镁转运蛋白。因此，我们的汇总数据发现了细菌中镁进口的一条新的、或许是广泛重要的途径。
Magnesium is an essential divalent metal that serves many cellular functions. While most divalent cations are maintained at relatively low intracellular concentrations, magnesium is maintained at a higher level (∼0.5–2.0 mM). Three families of transport proteins were previously identified for magnesium import: CorA, MgtE, and MgtA/MgtB P-type ATPases. In the current study, we find that expression of a bacterial protein unrelated to these transporters can fully restore growth to a bacterial mutant that lacks known magnesium transporters, suggesting it is a new importer for magnesium. We demonstrate that this transport activity is likely to be specific rather than resulting from substrate promiscuity because the proteins are incapable of manganese import. This magnesium transport protein is distantly related to the Nramp family of proteins, which have been shown to transport divalent cations but have never been shown to recognize magnesium. We also find gene expression of the new magnesium transporter to be controlled by a magnesium-sensing riboswitch. Importantly, we find additional examples of riboswitch-regulated homologues, suggesting that they are a frequent occurrence in bacteria. Therefore, our aggregate data discover a new and perhaps broadly important path for magnesium import and highlight how identification of riboswitch RNAs can help shed light on new, and sometimes unexpected, functions of their downstream genes. Magnesium ions are essential for life, and, correspondingly, all organisms must encode for proteins to transport them. Three classes of bacterial proteins (CorA, MgtE and MgtA/B) have previously been identified for transport of the ion. This current study introduces a new route of magnesium import, which, moreover, is unexpectedly provided by proteins distantly related to Natural resistance-associated macrophage proteins (Nramp). Nramp metal transporters are widespread in the three domains of life; however, most are assumed to function as transporters of transition metals such as manganese or iron. None of the previously characterized Nramps have been shown to transport magnesium. In this study, we demonstrate that certain bacterial proteins, distantly related to Nramp homologues, exhibit transport of magnesium. We also find that these new magnesium transporters are genetically controlled by a magnesium-sensing regulatory element. Importantly, we find numerous additional examples of similar genes sharing this regulatory arrangement, suggesting that these genes may be a frequent occurrence in bacteria, and may represent a class of magnesium transporters. Therefore, our aggregate data discover a new and perhaps broadly important path of magnesium import in bacteria.
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3
作者：
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