Stop codons preceded by rare arginine codons are efficient determinants of SsrA tagging in Escherichia coli
Stop codons preceded by rare arginine codons are efficient determinants of SsrA tagging in Escherichia coli
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DOI：
10.1073/pnas.052707199
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发表时间：
2002-03-19
影响因子：
11.1
通讯作者：
Sauer, RT
中科院分区：
文献类型：
--
作者：
Hayes, CS;Bose, B;Sauer, RT
SsrA或tmRNA质量控制系统在核糖体停留在mrna上时进行干预，并指导添加针对修饰多肽进行降解的c端肽标签。虽然在细胞中可以检测到数百种ssra标记的蛋白质，但当降解被阻止时，这些蛋白质中的大多数尚未被鉴定出来。因此，导致核糖体停滞和SsrA标记的mRNA序列决定因素知之甚少。大肠杆菌核糖激酶的SsrA标记发生在该蛋白C端或其附近的三个特定位点。标记位点对应于终止密码子上的核糖体和编码大肠杆菌核糖体激酶前端和c端残基Arg-307和Arg-309的稀有AGG密码子。对解码AGG的tRNA过表达的突变分析和研究表明，C端罕见的精氨酸密码子与相邻低效的UGA终止密码子结合，可能通过减缓翻译延伸和终止的速度来招募ssra标记系统。
The SsrA or tmRNA quality control system intervenes when ribosomes stall on mRNAs and directs the addition of a C-terminal peptide tag that targets the modified polypeptide for degradation. Although hundreds of SsrA-tagged proteins can be detected in cells when degradation is prevented, most of these species have not been identified. Consequently, the mRNA sequence determinants that cause ribosome stalling and SsrA tagging are poorly understood. SsrA tagging of Escherichia coli ribokinase occurs at three specific sites at or near the C terminus of this protein. The sites of tagging correspond to ribosome stalling at the termination codon and at rare AGG codons encoding Arg-307 and Arg-309, the antepenultimate and C-terminal residues of E. coli ribokinase. Mutational analyses and studies of the effects of overexpressing the tRNA that decodes AGG reveal that the combination of a rare arginine codon at the C terminus and the adjacent inefficient UGA termination codon act to recruit the SsrA-tagging system, presumably by slowing the rate of translation elongation and termination.