Synthesis and function of Queuosine in Bacteria

Queuosine(Q)是唯一可以挽救的tRNA修饰，将营养与翻译联系起来。 在真核生物中，抢救是合成Q的唯一途径，并提供前体碱基队列(Q 通过饮食或肠道微生物区系，直接插入到靶tRNA中。大约50%的肠子 微生物群模式物种被预测为营养缺陷型生物，必须挽救Q前体。在……里面 一般来说，细菌Q抢救酶的特性很差，特别是在革兰氏阳性 肠道和口腔微生物群中普遍存在的细菌。这个项目的重点是发现 Q抢救酶及新型Q合成和Q降解酶的性质 在与人类宿主相关的细菌中。我们还将详细探讨其生理作用。 Q在口腔主要病原菌变形链球菌中的作用初步结果提示Q 和/或Q前体在生物膜形成、能力和毒力中的作用。目标1的目标是 从实验上表征了两个主要的转运蛋白家族，预测它们将挽救Q前体： YhhQ/COG1738家族和能量耦合因子(ECF)底物特异性家族 (quet/qtrt)。事实上，这些家庭并不是功能相同的，成员似乎存在分歧， 根据物种的不同，运输不同Q前体的能力。目标2侧重于 催化最后一步反应的新型Q合成酶QUCH的生化性质 通过一种史无前例的反应进行生物合成。在目标1和目标2中，我们还将寻找 Q代谢中的“缺失”成分，如肠道微生物群中缺失的转运蛋白 细菌，如短杆菌和潜在的Q分解代谢基因。最终目标将探索 Q合成基因在变形链球菌检验其可能具有重要作用的假说中的作用 在管理能力方面。这项拟议的研究意义重大，因为微生物区系是一种 队列微量营养素的关键来源，从而充分表征了细菌Q合成， 人类相关细菌的抢救和降解途径是充分发挥作用的必要条件 了解这一关键资源的竞争动态并对其进行建模。此外，由于 变形链球菌在龋病进展中的重要性，了解 观察到Q合成基因在能力中的重要性将增加我们对关键 这种有机体如何在其口腔微生物群生态位中与其他有机体竞争的组成部分。

Queuosine (Q) is the only tRNA modification that can be salvaged, linking nutrition to translation. In eukaryotes salvage is the only Q synthesis route and the precursor base queuine (q) is provided by the diet or the gut microflora and directly inserted in target tRNAs. Around 50% of the gut microbiota model species are predicted to be auxotrophs and must salvage a Q precursor. In general, bacterial Q salvage enzymes are very poorly characterized, particularly in Gram-positive bacteria that are prevalent in the gut and oral microbiome. This project focuses on discovering and characterizing Q salvage enzymes as well as novel Q synthesis and Q degradation enzymes in bacteria associated with the human host. We will also explore in detail the physiological role of Q in the major oral pathogen Streptococcus mutans as preliminary results suggest a role of Q and/or Q precursors in biofilm formation, competence and virulence. The goal of Aim 1 is to experimentally characterize two main families of transporters predicted to salvage Q precursors: the YhhQ/COG1738 family and the Energy-Coupling Factor (ECF) substrate specificity families (QueT/QtrT). Indeed, these families are not iso-functional, and members seem to diverge, depending on the species, on the ability to transport different Q precursors. Aim 2 focuses on the biochemical characterization of the novel Q synthesis enzyme QueH that catalyzes the last step of biosynthesis through an unprecedented reaction. In both Aims 1 and 2, we will also hunt for “missing” components in Q metabolism such as missing transporters in prevalent gut microbiome bacteria such as Brevibacteria and potential Q catabolism genes. The final aim will explore the role of Q synthesis genes in S. mutans testing the hypothesis that they could have important roles in regulation of competence. The proposed research is significant because the microbiota is a key source for the queuine micronutrient, hence fully characterizing the bacterial Q synthesis, salvage and degradation pathways in human associated bacteria is a requirement to fully understand and model the competition dynamics for this key resource. In addition, because of the importance of S. mutans in dental caries progression, understanding the molecular basis for the observed importance of Q synthesis genes in competence will increase our understanding of key component of how this organism competes with others in its oral microbiome niche.