Methionine biosynthesis in Staphylococcus aureus is tightly controlled by a hierarchical network involving an initiator tRNA-specific T-box riboswitch.
Methionine biosynthesis in Staphylococcus aureus is tightly controlled by a hierarchical network involving an initiator tRNA-specific T-box riboswitch.
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DOI：
10.1371/journal.ppat.1003606
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发表时间：
2013-09
期刊：
影响因子：
6.7
通讯作者：
Ziebuhr W
中科院分区：
文献类型：
--
作者：
Schoenfelder SM;Marincola G;Geiger T;Goerke C;Wolz C;Ziebuhr W
与甲硫氨酸在蛋白质生物合成起始和许多细胞过程中的关键作用一致，大多数微生物已经进化出从头合成甲硫氨酸的机制。在这里，我们证明，在细菌病原体金黄色葡萄球菌，严格的反应控制CodY活性，T盒核糖开关和mRNA衰变机制的罕见组合调节蛋氨酸生物合成metICFE-mdh mRNA的合成和稳定性。与其他利用S盒核糖开关控制甲硫氨酸生物合成的芽孢杆菌目相比，S。金黄色葡萄球菌metICFE-mdh mRNA之前是含有T-box核糖开关的5′-未翻译的met前导RNA。有趣的是，这个T-box核糖开关被揭示为与不带电的引发剂甲酰甲硫氨酰-tRNA（tRNAi fMet）特异性相互作用，而延伸剂tRNAMet的结合被证明是弱的，这表明该系统在翻译起始控制中的推定的额外功能。met前导RNA/metICFE-mdh操纵子表达受结合met前导RNA启动子上游的阻遏物CodY的控制。作为严格响应的代谢应急回路的一部分，甲硫氨酸消耗激活RelA依赖性（p）ppGpp alarmone合成，从其结合位点释放CodY，从而激活met前导启动子。我们的数据进一步表明，metICFE-mdh转录的后续步骤受到5′ met前导相关的T-box核糖开关的严格控制，当甲硫氨酸存在时，该核糖开关介导过早的转录终止。如果甲硫氨酸供应有限，并且因此tRNAi fMet变得不带电荷，则全长met前导/metICFE-mdh mRNA被转录，其被涉及RNase J2的核酸酶快速降解。总之，这些数据表明葡萄球菌已经进化出特殊的机制来防止过量蛋氨酸的积累。我们推测，这种严格的控制可能反映了有限的代谢能力的葡萄球菌再利用蛋氨酸，除了芽孢杆菌，葡萄球菌缺乏蛋氨酸补救和多胺合成途径。因此，甲硫氨酸代谢可能是代谢的致命弱点，使该途径成为未来抗葡萄球菌药物开发的有趣靶点。原核生物代谢是我们理解细菌毒力和致病机制的关键，也是一个有巨大机会确定抗生素药物新靶点的领域。在这里，我们已经解决了迄今为止缺乏特点的调控蛋氨酸生物合成的S。金黄色。我们证明，葡萄球菌中的蛋氨酸生物合成控制显着不同，从其他芽孢杆菌的预测。值得注意的是，参与T盒而不是S盒核糖开关将葡萄球菌与其他细菌分开。我们首次提供了甲硫氨酰-tRNA特异性T盒与其同源tRNA相互作用的直接实验证据，并且将起始剂tRNAi fMet鉴定为特异性结合伴侣是一个意外的发现，其在葡萄球菌代谢中的确切功能仍有待建立。这些数据进一步表明，在葡萄球菌中，一系列调控元件被整合以形成一个分层网络，该网络优雅地限制了昂贵的（过量的）甲硫氨酸生物合成，同时可靠地确保以高度选择性的方式生产氨基酸。我们的研究结果开辟了一个前景，利用蛋氨酸的生物合成，特别是其T-盒介导的控制作为推定的目标（S）为未来的抗葡萄球菌治疗的发展。
In line with the key role of methionine in protein biosynthesis initiation and many cellular processes most microorganisms have evolved mechanisms to synthesize methionine de novo. Here we demonstrate that, in the bacterial pathogen Staphylococcus aureus, a rare combination of stringent response-controlled CodY activity, T-box riboswitch and mRNA decay mechanisms regulate the synthesis and stability of methionine biosynthesis metICFE-mdh mRNA. In contrast to other Bacillales which employ S-box riboswitches to control methionine biosynthesis, the S. aureus metICFE-mdh mRNA is preceded by a 5′-untranslated met leader RNA harboring a T-box riboswitch. Interestingly, this T-box riboswitch is revealed to specifically interact with uncharged initiator formylmethionyl-tRNA (tRNAi fMet) while binding of elongator tRNAMet proved to be weak, suggesting a putative additional function of the system in translation initiation control. met leader RNA/metICFE-mdh operon expression is under the control of the repressor CodY which binds upstream of the met leader RNA promoter. As part of the metabolic emergency circuit of the stringent response, methionine depletion activates RelA-dependent (p)ppGpp alarmone synthesis, releasing CodY from its binding site and thereby activating the met leader promoter. Our data further suggest that subsequent steps in metICFE-mdh transcription are tightly controlled by the 5′ met leader-associated T-box riboswitch which mediates premature transcription termination when methionine is present. If methionine supply is limited, and hence tRNAi fMet becomes uncharged, full-length met leader/metICFE-mdh mRNA is transcribed which is rapidly degraded by nucleases involving RNase J2. Together, the data demonstrate that staphylococci have evolved special mechanisms to prevent the accumulation of excess methionine. We hypothesize that this strict control might reflect the limited metabolic capacities of staphylococci to reuse methionine as, other than Bacillus, staphylococci lack both the methionine salvage and polyamine synthesis pathways. Thus, methionine metabolism might represent a metabolic Achilles' heel making the pathway an interesting target for future anti-staphylococcal drug development. Prokaryote metabolism is key for our understanding of bacterial virulence and pathogenesis and it is also an area with huge opportunity to identify novel targets for antibiotic drugs. Here, we have addressed the so far poorly characterized regulation of methionine biosynthesis in S. aureus. We demonstrate that methionine biosynthesis control in staphylococci significantly differs from that predicted for other Bacillales. Notably, involvement of a T-box instead of an S-box riboswitch separates staphylococci from other bacteria in the order. We provide, for the first time, direct experimental proof for an interaction of a methionyl-tRNA-specific T-box with its cognate tRNA, and the identification of initiator tRNAi fMet as the specific binding partner is an unexpected finding whose exact function in Staphylococcus metabolism remains to be established. The data further suggest that in staphylococci a range of regulatory elements are integrated to form a hierarchical network that elegantly limits costly (excess) methionine biosynthesis and, at the same time, reliably ensures production of the amino acid in a highly selective manner. Our findings open a perspective to exploit methionine biosynthesis and especially its T-box-mediated control as putative target(s) for the development of future anti-staphylococcal therapeutics.
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影响因子：
4.4
作者：
Nagarajan, Vijayaraj;Elasri, Mohamed O.
通讯作者：
Elasri, Mohamed O.
DOI：
10.1073/pnas.85.4.1033
发表时间：
1988-02-01
影响因子：
11.1
作者：
SAMPSON, JR;UHLENBECK, OC
通讯作者：
UHLENBECK, OC
影响因子：
3.2
作者：
Pohl, Konstanze;Francois, Patrice;Wolz, Christiane
通讯作者：
Wolz, Christiane
影响因子：
4.2
作者：
Sekowska, A;Dénervaud, V;Danchin, A
通讯作者：
Danchin, A
影响因子：
3.6
作者：
Maeder, Ulrike;Zig, Lena;Putzer, Harald
通讯作者：
Putzer, Harald