Initiation of protein synthesis in mammalian cells with codons other than AUG and amino acids other than methionine
Initiation of protein synthesis in mammalian cells with codons other than AUG and amino acids other than methionine
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DOI：
10.1128/mcb.18.9.5140
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发表时间：
1998-09-01
影响因子：
5.3
通讯作者：
Rajbhandary, UL
中科院分区：
文献类型：
--
作者：
Drabkin, HJ;Rajbhandary, UL
蛋白质的合成一般都是由甲硫氨酸开始的。在大肠杆菌中，对起始甲硫氨酸tRNA的反密码子序列突变体的研究表明，蛋白质合成可以由几种其他氨基酸起始。然而，在真核系统中，发现用异亮氨酸氨酰化的酵母起始剂tRNA在哺乳动物细胞提取物中的起始中是无活性的。这一发现提出了一个问题：蛋氨酸是否是真核生物中唯一能够启动蛋白质合成的氨基酸。在这项工作中，我们研究了活动，在启动，四个不同的反密码子序列突变体的人启动子tRNA在哺乳动物COS 1细胞，使用报告基因携带突变的起始密码子是互补的tRNA反密码子。使用的突变体tRNA被谷氨酰胺、甲硫氨酸和缬氨酸氨酰化。我们的研究结果表明，在相应的突变起始tRNA的存在下，AGG和GUC可以启动蛋白质合成在COS 1细胞与蛋氨酸和缬氨酸，分别。CAG启动蛋白质合成与谷氨酰胺，但非常差，而UAG不能用于启动蛋白质合成与谷氨酰胺。我们讨论了潜在的应用程序的突变启动tRNA依赖启动蛋白质合成的密码子以外的AUG研究在哺乳动物细胞中蛋白质合成启动的许多有趣的方面。
Protein synthesis is initiated universally with the amino acid methionine. In Escherichia coli, studies with anticodon sequence mutants of the initiator methionine tRNA have shown that protein synthesis can be initiated with several other amino acids. In eukaryotic systems, however, a yeast initiator tRNA aminoacylated with isoleucine was found to be inactive in initiation in mammalian cell extracts. This finding raised the question of whether methionine is the only amino acid capable of initiation of protein synthesis in eukaryotes. In this work, we studied the activities, in initiation, of four different anticodon sequence mutants of human initiator tRNA in mammalian COS1 cells, using reporter genes carrying mutations in the initiation codon that are complementary to the tRNA anticodons. The mutant tRNAs used are aminoacylated with glutamine, methionine, and valine. Our results show that in the presence of the corresponding mutant initiator tRNAs, AGG and GUC can initiate protein synthesis in COS1 cells with methionine and valine, respectively. CAG initiates protein synthesis with glutamine but extremely poorly, whereas UAG could not be used to initiate protein synthesis with glutamine. We discuss the potential applications of the mutant initiator tRNA-dependent initiation of protein synthesis with codons other than AUG for studying the many interesting aspects of protein synthesis initiation in mammalian cells.