A Rhodobacter sphaeroides protein mechanistically similar to Escherichia coli DksA regulates photosynthetic growth.
A Rhodobacter sphaeroides protein mechanistically similar to Escherichia coli DksA regulates photosynthetic growth.
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DOI：
10.1128/mbio.01105-14
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发表时间：
2014-04-29
期刊：
影响因子：
6.4
通讯作者：
Ross W
中科院分区：
文献类型：
--
作者：
Lennon CW;Lemmer KC;Irons JL;Sellman MI;Donohue TJ;Gourse RL;Ross W
DksA是一种全局调节蛋白，与alarmone ppGpp一起，是γ-变形杆菌大肠杆菌对营养饥饿的“严格反应”和生长条件之间更温和的转变所需的。DksA直接或间接地调节数百个基因的表达。缺乏DksA同源物的突变体在其他γ-变形菌中也表现出多效性表型。在这里，我们分析了DksA同源RSP 2654在更远的相关的球形红细菌，一个alphaproteobacterium。RSP 2654与大肠杆菌DksA具有42%的同一性，并且长度相似，但缺乏大肠杆菌DksA球状结构域的锌指基序。RSP 2654基因的缺失导致光合生长缺陷、氨基酸利用受损和脂肪酸含量增加。RSP 2654补充了缺乏dksA基因的大肠杆菌菌株的生长和调控缺陷，并与大肠杆菌DksA类似地在体外用大肠杆菌RNA聚合酶（RNAP）调节转录。RSP 2654在体外与来自大肠杆菌或类球形红球菌的RNAP单独或与ppGpp协同降低RNAP-启动子复合物的稳定性，表明即使其与大肠杆菌DksA（DksAEc）具有有限的序列同一性，但其以类似的机制方式发挥作用。因此，我们将RSP 2654蛋白命名为DksARsp。我们的工作表明，DksARsp具有独特的和重要的生理作用，在alphaproteobacteria和DksA和ppGpp之间的协同作用机制的结构和功能的关系，将是有用的理解DksA。DksA的作用主要在γ-变形菌中进行了分析，在γ-变形菌中，DksA在控制翻译装置的合成和氨基酸生物合成中的作用是最好的理解。我们的工作表明，DksA在α-变形菌中起着独特而重要的生理作用，包括控制Rhodobacter sphaeroides的光合作用。DksARsp的研究应该有助于理解蛋白质的结构-功能关系，包括那些在DksA和ppGpp之间的协同作用中发挥作用的蛋白质。
DksA is a global regulatory protein that, together with the alarmone ppGpp, is required for the “stringent response” to nutrient starvation in the gammaproteobacterium Escherichia coli and for more moderate shifts between growth conditions. DksA modulates the expression of hundreds of genes, directly or indirectly. Mutants lacking a DksA homolog exhibit pleiotropic phenotypes in other gammaproteobacteria as well. Here we analyzed the DksA homolog RSP2654 in the more distantly related Rhodobacter sphaeroides, an alphaproteobacterium. RSP2654 is 42% identical and similar in length to E. coli DksA but lacks the Zn finger motif of the E. coli DksA globular domain. Deletion of the RSP2654 gene results in defects in photosynthetic growth, impaired utilization of amino acids, and an increase in fatty acid content. RSP2654 complements the growth and regulatory defects of an E. coli strain lacking the dksA gene and modulates transcription in vitro with E. coli RNA polymerase (RNAP) similarly to E. coli DksA. RSP2654 reduces RNAP-promoter complex stability in vitro with RNAPs from E. coli or R. sphaeroides, alone and synergistically with ppGpp, suggesting that even though it has limited sequence identity to E. coli DksA (DksAEc), it functions in a mechanistically similar manner. We therefore designate the RSP2654 protein DksARsp. Our work suggests that DksARsp has distinct and important physiological roles in alphaproteobacteria and will be useful for understanding structure-function relationships in DksA and the mechanism of synergy between DksA and ppGpp. The role of DksA has been analyzed primarily in the gammaproteobacteria, in which it is best understood for its role in control of the synthesis of the translation apparatus and amino acid biosynthesis. Our work suggests that DksA plays distinct and important physiological roles in alphaproteobacteria, including the control of photosynthesis in Rhodobacter sphaeroides. The study of DksARsp, should be useful for understanding structure-function relationships in the protein, including those that play a role in the little-understood synergy between DksA and ppGpp.