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相关概念视频

Initiation of Translation02:33

Initiation of Translation

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Initiating translation is complex because it involves multiple molecules. Initiator tRNA, ribosomal subunits, and eukaryotic initiation factors (eIFs) are all required to assemble on the initiation codon of mRNA. This process consists of several steps that are mediated by different eIFs.
First, the initiator tRNA must be selected from the pool of elongator tRNAs by eukaryotic initiation factor 2 (eIF2). The initiator tRNA (Met-tRNAi) has conserved sequence elements including modified bases at...
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Initiation of Translation02:33

Initiation of Translation

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Leaky Scanning02:28

Leaky Scanning

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During most eukaryotic translation processes, the small 40S ribosome subunit scans an mRNA from its 5' end until it encounters the first start AUG codon. The large 60S ribosomal subunit then joins the smaller one to initiate protein synthesis. The location of the translation initiation is largely determined by the nucleotides near the start codon as there may be multiple translation initiation sites present on the mRNA.  Marilyn Kozak discovered that the sequence RCCAUGG (where R...
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Translation in Prokaryotes01:29

Translation in Prokaryotes

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Prokaryote translation is a complex, highly coordinated process that converts genetic information from mRNA into functional proteins. It involves three stages: initiation, elongation, and termination, each facilitated by specific molecular components.Initiation of TranslationThe process begins with the assembly of the ribosomal subunits and initiation factors on the mRNA. In bacteria, the 30S ribosomal subunit recognizes the Shine-Dalgarno sequence in the mRNA, a conserved region upstream of...
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Improving Translational Accuracy02:07

Improving Translational Accuracy

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Base complementarity between the three base pairs of mRNA codon and the tRNA anticodon is not a failsafe mechanism. Inaccuracies can range from a single mismatch to no correct base pairing at all. The free energy difference between the correct and nearly correct base pairs can be as small as 3 kcal/ mol. With complementarity being the only proofreading step, the estimated error frequency would be one wrong amino acid in every 100 amino acids incorporated. However, error frequencies observed in...
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pre-mRNA Processing02:01

pre-mRNA Processing

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In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or pre-mRNA to distinguish it from mature mRNA.
Once about 20-40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes adds a “cap” to the 5’ end of the growing transcript. In this process, a 5’ phosphate is replaced by modified guanosine that has a methyl group attached to it (7-Methyl...
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Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs
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结构上的变化使得真核体的翻译启动复合体能够识别起始编码子.

Tanweer Hussain1, Jose L Llácer1, Israel S Fernández1

  • 1MRC Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.

Cell
|November 24, 2014
PubMed
概括

细胞翻译启动涉及启动器tRNA采用POUT对mRNA扫描的构成. 在AUG识别后,它以PIN状态进行异构,稳定了密码体-抗密码体双重并促进了启动密码体的识别.

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科学领域:

  • 分子生物学分子生物学
  • 结构生物学 结构生物学
  • 生物化学 生物化学

背景情况:

  • 细胞翻译启动是一个复杂的过程,涉及多种蛋白质因子和40S核糖体子单元.
  • 发起者tRNA最初以非正规的POUT构造结合,允许进行mRNA扫描.
  • 启动编码子识别触发了PIN状态的构造变化,这对于翻译至关重要.

研究的目的:

  • 阐明在真核细胞翻译启动过程中PIN状态的结构基础.
  • 使用冷电子显微镜可视化酵母预启动复合物与PIN状态的启动器tRNA.
  • 了解启动因子在稳定启动符号识别复合体中的作用.

主要方法:

  • 酵母预启动复合物的冷电子显微镜 (cryo-EM) 重建.
  • 高分辨率结构分析 (4.0 Å分辨率).

主要成果:

  • 确定了酵母预启动复合物与PIN状态的启动器tRNA的冷EM结构.
  • 细胞启动因子1A (eIF1A) 的N端尾稳定了子-子双重.
  • 观察到真核启动因子1 (eIF1) 和真核启动因子2 (eIF2) 的形状变化,有助于eIF1释放和启动编码子识别.
  • mRNA与eIF2,eIF1A和核糖体元素相互作用,使背景核酸识别成为可能.

结论:

  • 通过涉及eIF1A和关键核糖体元素的相互作用来稳定PIN状态.
  • 在eIF1和eIF2中的结构重组对于从扫描到开始编码子识别的过渡至关重要.
  • 该结构提供了关于核糖体如何在翻译启动过程中识别AUG起始编码子及其周围环境的见解.