N-(PURIN-6-YLCARBAMOYL)THREONINE - BIOSYNTHESIS IN-VITRO IN TRANSFER-RNA BY AN ENZYME PURIFIED FROM ESCHERICHIA-COLI
N-(PURIN-6-YLCARBAMOYL)THREONINE - BIOSYNTHESIS IN-VITRO IN TRANSFER-RNA BY AN ENZYME PURIFIED FROM ESCHERICHIA-COLI
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DOI：
10.1016/0014-5793(74)80135-3
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发表时间：
1974-01-01
期刊：
影响因子：
3.5
通讯作者：
SOLL, D
中科院分区：
文献类型：
--
作者：
KORNER, A;SOLL, D
在原核生物和真核生物中，发现修饰的核苷N-（嘌呤-6-基氨基甲酰基）-苏氨酸（t6 A）或该核苷的衍生物邻近于tRNA中反密码子的3 '末端，所述tRNA响应于从腺嘌呤开始的密码子[1 -4]。虽然这种修饰的核苷在tRNA的生物学功能中的作用尚不清楚，但体外实验[S]表明这种修饰的核苷可能负责正确识别以腺嘌呤开始的密码子，或负责tRNA在核糖体上的正确定位。这种修饰的核苷属于超修饰核苷类，更复杂的修饰核苷[6，7]带有反应性侧链。因此，它的生物合成可能涉及一个以上的步骤。大鼠[8]和大肠杆菌中t6 A生物合成的体内研究。coli [8，9]的结果表明，@ A的苏氨酸部分来源于游离苏氨酸。有了这些知识，我们开始研究放射性苏氨酸在体外掺入含有t6 A的tRNA。对于这些研究，需要通常含有t6 A但可以在没有这种修饰的情况下产生的tRNA底物。最近，一种携带E.已经描述了tRNAThr、tRNATYr和tRNAG种的大肠杆菌基因[10]。当这种噬菌体的溶原细胞被诱导时，由噬菌体基因编码的tRNA以增加的量产生，但通常是修饰不足的（参见参考文献1）。[10，111）。由于tRNATh含有@ A [1 -4]，我们使用来自诱导的E.该噬菌体的大肠杆菌溶原作为检测酶的底物
The modified nucleoside N-(purin-6-ylcarbamoyl)-threonine (t6A), or derivatives of this nucleoside, is found adjacent to the 3’end of the anticodon in tRNAs responding to codons beglning with adenine, both in prokaryotic and eukaryotic organisms [l-4]. While the role of this modified nucleoside in the biological functions of tRNA ia unknown, in vitro experiments [S] suggest this modified nucleoside may be responsible for correct recognition of codoas that begin with adenine, or for correct orientation of the tRNA on the ribosome. This modified nucleoside belongs to the class of hypermodified nucleosides, more complex modified nucleosides [6, 7] bearing a reactive side chain. Consequently, its biosynthesis may involve more than one step. In vivo studies on the biosynthesis of t6A in the rat [8] and E. coli [8, 9] showed that the threonine moiety of@ A is derived from free threonine. With this knowledge we set out to study the in vitro incorporation of radioactive threonine into t6A containing tRNA. For these studies a tRNA substrate is required that normally contains t6A but which can be produced lacking this modification. Recently, a defective X $80 hybrid transducing phage that carries the E. coli genes for a tRNAThr, a tRNATYr and a tRNAG@ species has been described [IO]. When a lysogen of this phage is induced, the tRNAs coded by the phage genes are produced in increased amounts but are often undermodified (see refs.[10, 111). Since tRNATh contains@ A [l-4] we used the tRNA from an induced E. coli lysogen of this phage as a substrate for detection of the enzyme (s)