The Escherichia coli COG1738 Member YhhQ Is Involved in 7-Cyanodeazaguanine (preQ₀) Transport.
The Escherichia coli COG1738 Member YhhQ Is Involved in 7-Cyanodeazaguanine (preQ₀) Transport.
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DOI：
10.3390/biom7010012
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发表时间：
2017-02-08
期刊：
影响因子：
5.5
通讯作者：
de Crécy-Lagard V
中科院分区：
文献类型：
--
作者：
Zallot R;Yuan Y;de Crécy-Lagard V
肌苷（Q）是tRNA中摆动碱基与GUN反密码子的复杂修饰。完整的Q生物合成途径已在大肠杆菌中阐明。FolE、QueD、QueE和QueC参与鸟苷三磷酸（GTP）转化为7-氰基-7-脱氮鸟嘌呤（preQ 0），这是一种因其在tRNA和DNA修饰和次级代谢中的中心作用而越来越受关注的中间体。然后QueF将preQ 0还原为7-氨甲基-7-脱氮鸟嘌呤（preQ 1）。PreQ 1通过tRNA鸟嘌呤（34）转糖基酶（TGT）插入tRNA中。通过涉及QueA和QueG或QueH的两个附加步骤，插入的碱基preQ 1最终成熟为Q。大多数真细菌具有全套的Q合成基因，并且被预测为从头合成Q。然而，一些细菌仅编码参与preQ 0合成下游途径的后半部分的酶，包括特征酶TGT。观察到queF、tgt、queA和queG或queH基因的不同分布模式，表明preQ 0、preQ 1甚至队列碱基在特定生物体中被挽救。这种补救途径需要存在尚未鉴定的特异性7-脱氮嘌呤转运蛋白。通过比较基因组学分析，COG 1738家族被鉴定为原核生物中缺失的preQ 0/preQ 1转运蛋白的候选者。Q前体补救的存在首次在体内细菌中通过间接测定得到证实。在大肠杆菌中实验验证了COG 1738参与Q前体的补救，其中表明COG 1738家族成员YhhQ对preQ 0转运至关重要。
Queuosine (Q) is a complex modification of the wobble base in tRNAs with GUN anticodons. The full Q biosynthesis pathway has been elucidated in Escherichia coli. FolE, QueD, QueE and QueC are involved in the conversion of guanosine triphosphate (GTP) to 7-cyano-7-deazaguanine (preQ0), an intermediate of increasing interest for its central role in tRNA and DNA modification and secondary metabolism. QueF then reduces preQ0 to 7-aminomethyl-7-deazaguanine (preQ1). PreQ1 is inserted into tRNAs by tRNA guanine(34) transglycosylase (TGT). The inserted base preQ1 is finally matured to Q by two additional steps involving QueA and QueG or QueH. Most Eubacteria harbor the full set of Q synthesis genes and are predicted to synthesize Q de novo. However, some bacteria only encode enzymes involved in the second half of the pathway downstream of preQ0 synthesis, including the signature enzyme TGT. Different patterns of distribution of the queF, tgt, queA and queG or queH genes are observed, suggesting preQ0, preQ1 or even the queuine base being salvaged in specific organisms. Such salvage pathways require the existence of specific 7-deazapurine transporters that have yet to be identified. The COG1738 family was identified as a candidate for a missing preQ0/preQ1 transporter in prokaryotes, by comparative genomics analyses. The existence of Q precursor salvage was confirmed for the first time in bacteria, in vivo, through an indirect assay. The involvement of the COG1738 in salvage of a Q precursor was experimentally validated in Escherichia coli, where it was shown that the COG1738 family member YhhQ is essential for preQ0 transport.