SecM暂停核糖体多步翻译延伸机制研究
发布时间：2019-05-23 01:39
【摘要】：“中心法则”中将遗传信息从mRNA传递到蛋白质这一过程,主要由大分子机器核糖体负责完成。核糖体是整个蛋白质质量控制过程的中心,通过校对蛋白合成和下游基因启动,来调控新生肽链的命运。核糖体翻译过程中,一系列核糖体蛋白结合因子作用于核糖体,使核糖体以不恒定的速率合成新生肽链,并对新生肽链进行修饰和辅助折叠,从而参与蛋白质质量控制。越来越多的研究发现,新生肽链在合成过程中,会被暂停于核糖体肽链输出通道,与核糖体组分相互作用参与共转录基因的表达调控。大肠杆菌中,SecM是一种170个氨基酸长度的分泌型蛋白,它的C端序列会调控核糖体翻译暂停,启动下游基因的表达。生化与结构研究揭示SecM的C端17个氨基酸序列(150FSTPVWISQAQGIRAGP166)能与23S rRNA和核糖体蛋白uL22、uL4相互作用,以紧凑的构象存在肽链输出通道中,引起肽基转移酶中心(PTC中心)失活从而导致翻译暂停。然而,SecM诱导翻译暂停的分子机制仍然不是很清楚。更甚地是,越来越多的研究发现SecM诱导的翻译暂停可能是一个动态变化的过程。因此,我们采用冷冻电子显微镜技术来分析SecM暂停核糖体翻译的机制,并解析出分辨率在3.5~3.7?的两种翻译暂停复合物冷冻电镜结构。通过生化与结构分析,我们发现SecM暂停翻译存在两种不同的机制,并且会暂停在翻译延伸不同阶段。一种是SecM暂停核糖体于非旋转状态,使肽基转移酶中心失活,不利于氨基-tRNA定位到50S大亚基的A位点并进行自调整。另一种是SecM暂停核糖体于旋转状态,延长新生肽链-tRNA从杂交A/P位点易位到P/P位点过程。两种暂停机制中,SecM暂停序列中R163都起到关键作用,在暂停序列中其他氨基酸的帮助下,定位于特定位置并与通道组分相互作用,引起50S构象变化而不利于翻译延伸。综上所述,本研究首次提出SecM暂停核糖体翻译存在两种机制,揭示了SecM与核糖体组分相互作用,对翻译延伸进行连续多步调控的细节。结合已报道的研究,包括抗生素、引导肽等在内的新生肽链和/或小分子配体通过不同机制诱导核糖体构象变化,从而微调核糖体翻译速率。
[Abstract]:The process of transferring genetic information from mRNA to protein in the Central Law is mainly done by macromolecular machine ribosomes. Ribosome is the center of the whole protein quality control process. Through proofreading protein synthesis and downstream gene initiation, the fate of new peptide chain is regulated. In the process of ribosomal translation, a series of ribosomal protein binding factors act on ribosomes, which make ribosomes synthesize new peptide chains at a constant rate, and modify and assist folding of new peptide chains, thus participating in protein quality control. More and more studies have found that the new peptide chain will be suspended in the ribosomal peptide chain output channel in the process of synthesis, and the interaction with ribosomal components will participate in the regulation of co-transcriptional gene expression. In E. coli, SecM is a secretory protein with the length of 170amino acids. Its C-terminal sequence can regulate ribosomal translation pause and initiate the expression of downstream genes. Biochemical and structural studies have revealed that the C-terminal 17 amino acid sequence (150FSTPVWISQAQGIRAGP166) of SecM can interact with 23s rRNA and ribosomal protein uL22,uL4, and exist in the peptide chain output channel in a compact configuration. It leads to the inactivation of peptidytransferase center (PTC center), which leads to the suspension of translation. However, the molecular mechanism of SecM induced translation suspension is still unclear. More and more studies have found that SecM-induced translation pauses may be a dynamic process. Therefore, we use frozen electron microscope to analyze the mechanism of SecM suspending ribosomal translation, and analyze the resolution of 3.5 鈮，
本文编号：2483478
[Abstract]:The process of transferring genetic information from mRNA to protein in the Central Law is mainly done by macromolecular machine ribosomes. Ribosome is the center of the whole protein quality control process. Through proofreading protein synthesis and downstream gene initiation, the fate of new peptide chain is regulated. In the process of ribosomal translation, a series of ribosomal protein binding factors act on ribosomes, which make ribosomes synthesize new peptide chains at a constant rate, and modify and assist folding of new peptide chains, thus participating in protein quality control. More and more studies have found that the new peptide chain will be suspended in the ribosomal peptide chain output channel in the process of synthesis, and the interaction with ribosomal components will participate in the regulation of co-transcriptional gene expression. In E. coli, SecM is a secretory protein with the length of 170amino acids. Its C-terminal sequence can regulate ribosomal translation pause and initiate the expression of downstream genes. Biochemical and structural studies have revealed that the C-terminal 17 amino acid sequence (150FSTPVWISQAQGIRAGP166) of SecM can interact with 23s rRNA and ribosomal protein uL22,uL4, and exist in the peptide chain output channel in a compact configuration. It leads to the inactivation of peptidytransferase center (PTC center), which leads to the suspension of translation. However, the molecular mechanism of SecM induced translation suspension is still unclear. More and more studies have found that SecM-induced translation pauses may be a dynamic process. Therefore, we use frozen electron microscope to analyze the mechanism of SecM suspending ribosomal translation, and analyze the resolution of 3.5 鈮，
本文编号：2483478
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