A post-translational modification in the GGQ motif of RF2 from Escherichia coli stimulates termination of translation
A post-translational modification in the GGQ motif of RF2 from Escherichia coli stimulates termination of translation
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DOI：
10.1093/emboj/19.24.6900
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发表时间：
2000-12-15
期刊：
影响因子：
11.4
通讯作者：
Ehrenberg, M
中科院分区：
文献类型：
--
作者：
Dinçbas-Renqvist, V;Engström, Å;Ehrenberg, M
在大肠杆菌中普遍保守的释放因子2(RF2)的GGQ序列中发现了一个影响翻译终止率的翻译后修饰，该序列被认为模仿tRNA分子的CCA末端。质谱分析和Edman降解结果表明，谷氨酰胺在252位发生了N-5-甲基化。RF2的过度表达产生了缺乏甲基化的蛋白质。来自E.coliK12的RF2的独特之处在于在GGQ基序附近有Thr246，而所有其他测序的细菌1类RFs都含有丙氨酸或丝氨酸，来自E.coliB和MRE600菌株的prfB基因测序表明，残基246编码为丙氨酸，与K12 RF2相比，Thr246降低了RF2依赖的终止效率，特别是对于短肽-tRNAs，Gln252的甲基化提高了RF2的终止效率，而与246位氨基酸的同一性无关，我们认为先前观察到的过量生产E.ColiK12 RF2的致死效应是通过缺乏Gln252甲基化和Thr246取代丙氨酸而产生的。
A post-translational modification affecting the translation termination rate was identified in the universally conserved GGQ sequence of release factor 2 (RF2) from Escherichia coli, which is thought to mimic the CCA end of the tRNA molecule. It was shown by mass spectrometry and Edman degradation that glutamine in position 252 is N-5-methylated. Overexpression of RF2 yields protein lacking the methylation. RF2 from E.coli K12 is unique in having Thr246 near the GGQ motif, where all other sequenced bacterial class 1 RFs have alanine or serine, Sequencing the prfB gene from E.coli B and MRE600 strains showed that residue 246 is coded as alanine, in contrast to K12 RF2, Thr246 decreases RF2-dependent termination efficiency compared with Ala246, especially for short peptidyl-tRNAs, Methylation of Gln252 increases the termination efficiency of RF2, irrespective of the identity of the amino acid in position 246, We propose that the previously observed lethal effect of overproducing E.coli K12 RF2 arises through accumulating the defects due to lack of Gln252 methylation and Thr246 in place of alanine.