Identification of a radical SAM enzyme involved in the synthesis of archaeosine
Identification of a radical SAM enzyme involved in the synthesis of archaeosine
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DOI：
10.1038/s41589-019-0390-7
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发表时间：
2019-12-01
影响因子：
14.8
通讯作者：
Ohno，Satoshi
中科院分区：
文献类型：
--
作者：
Yokogawa，Takashi;Nomura，Yuichiro;Ohno，Satoshi
古核苷（G+），7-甲脒基-7-脱氮鸟苷，是一种存在于tRNA第15位的古细菌特异性修饰核苷。在广古菌中，由古菌tRNA-鸟嘌呤转糖基酶（ArcTGT）合成的含7-氰基-7-脱氮鸟嘌呤（preQ 0）的tRNA（q 0 N-tRNA）被ArcTGT的副产物ArcS转化为含G+的tRNA（G+-tRNA）。然而，我们发现几种广古菌ArcSs具有赖氨酸转移活性，以q 0 N-tRNA形成q 0 kN-tRNA，其具有前Q 0赖氨酸加合物作为碱。通过比较基因组学和生物化学实验，我们发现ArcS与一种名为RaSEA的自由基S-腺苷甲硫氨酸（SAM）酶形成了一种强大的复合物。在SAM和赖氨酸存在下，ArcS-RaSEA复合物通过q 0 kN-tRNA将q 0 N-tRNA厌氧转化为G+-tRNA。我们认为ArcS和RaSEA分别是古核苷合成酶的α亚基（赖氨酸转移酶）和β亚基（q 0 kN-tRNA裂解酶）。
Archaeosine (G+), 7-formamidino-7-deazaguanosine, is an archaea-specific modified nucleoside found at the 15th position of tRNAs. In Euryarchaeota, 7-cyano-7-deazaguanine (preQ0)-containing tRNA (q0N-tRNA), synthesized by archaeal tRNA-guanine transglycosylase (ArcTGT), has been believed to be converted to G+-containing tRNA (G+-tRNA) by the paralog of ArcTGT, ArcS. However, we found that several euryarchaeal ArcSs have lysine transfer activity to q0N-tRNA to form q0kN-tRNA, which has a preQ0lysine adduct as a base. Through comparative genomics and biochemical experiments, we found that ArcS forms a robust complex with a radicalS-adenosylmethionine (SAM) enzyme named RaSEA. The ArcS–RaSEA complex anaerobically converted q0N-tRNA to G+-tRNA in the presence of SAM and lysine via q0kN-tRNA. We propose that ArcS and RaSEA should be considered an archaeosine synthase α-subunit (lysine transferase) and β-subunit (q0kN-tRNA lyase), respectively.