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関連する概念動画

Improving Translational Accuracy02:07

Improving Translational Accuracy

11.8K
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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tRNA Activation02:26

tRNA Activation

19.6K
Aminoacyl-tRNA synthetases are present in both eukaryotes and bacteria. Though eukaryotes have 20 different aminoacyl-tRNA synthetases to couple to 20 amino acids, many bacteria do not have genes for all of these aminoacyl-tRNA synthetases. Despite this, they still use all 20 amino acids to synthesize their proteins. For instance, some bacteria do not have the gene encoding the enzyme that couples glutamine with its partner tRNA. In these organisms, one enzyme adds glutamic acid to all of the...
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Transfer RNA Synthesis02:36

Transfer RNA Synthesis

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One of the unique features of tRNA is the presence of modified bases. In some tRNAs, modified bases account for nearly 20% of the total bases in the molecule. Altogether, these unusual bases protect the tRNA from enzymatic degradation by RNases.
Each of these chemical modifications is carried by a specific enzyme, post-transcription. All of these enzymes have unique base and site-specificity. Methylation, the most common chemical modification, is carried by at least nine different enzymes, with...
12.1K
Nonsense-mediated mRNA Decay02:27

Nonsense-mediated mRNA Decay

10.7K
The Upf proteins that carry out nonsense-mediated decay (NMD) are found in all eukaryotic organisms, including humans. Each protein has an individual role, but they need to work in collaboration. Upf1 is an ATP-dependent RNA helicase that unwinds the RNA helix. Because Upf1 can unwind any RNA, Upf2 and Upf3 are required to help Upf1 discriminate between nonsense and normal mRNAs.
Usually, Upf3 binds to an Exon Junction Complex (EJC) at mRNA splice sites. If a ribosome fully translates the mRNA,...
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Mutations01:39

Mutations

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Overview
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Translation01:31

Translation

142.8K
Lesson: Translation
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes the final step in the expression of genes. This process is carried out by ribosomes, complexes of protein and specialized RNA molecules. Ribosomes, transfer RNA (tRNA), and other proteins produce a chain of amino acids—the polypeptide—as the end product of translation.
Translation Produces the Building Blocks of...
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関連する実験動画

Updated: Aug 14, 2025

Removal of an Internal Translational Start Site from mRNA While Retaining Expression of the Full-Length Protein
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短いtRNAの抗コドン幹と変異したeRF1は,コドン再配分を停止します.

Ambar Kachale1,2, Zuzana Pavlíková3, Anna Nenarokova1,2,4

  • 1Institute of Parasitology, Biology Centre, Czech Academy of Sciences, České Budějovice, Czech Republic.

Nature
|January 11, 2023
PubMed
まとめ

プロティストは ストップコドンを再配置します この研究は,tRNAの改変と放出因子の変異を含む普遍的なメカニズムを明らかにし,コドン再配分と遺伝子発現の調節を止めることができます.

さらに関連する動画

Studying Ribonucleotide Incorporation: Strand-specific Detection of Ribonucleotides in the Yeast Genome and Measuring Ribonucleotide-induced Mutagenesis
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Studying Ribonucleotide Incorporation: Strand-specific Detection of Ribonucleotides in the Yeast Genome and Measuring Ribonucleotide-induced Mutagenesis

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Residue-Specific Exchange of Proline by Proline Analogs in Fluorescent Proteins: How "Molecular Surgery" of the Backbone Affects Folding and Stability
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Residue-Specific Exchange of Proline by Proline Analogs in Fluorescent Proteins: How "Molecular Surgery" of the Backbone Affects Folding and Stability

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関連する実験動画

Last Updated: Aug 14, 2025

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Studying Ribonucleotide Incorporation: Strand-specific Detection of Ribonucleotides in the Yeast Genome and Measuring Ribonucleotide-induced Mutagenesis
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Residue-Specific Exchange of Proline by Proline Analogs in Fluorescent Proteins: How "Molecular Surgery" of the Backbone Affects Folding and Stability
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科学分野:

  • 分子生物学
  • 遺伝学
  • 進化生物学

背景:

  • 標準的な遺伝子コードは 特定のコードンを 翻訳中に停止信号として使います
  • いくつかの生物,特に原生体は,これらのストップコドンをアミノ酸をエンコードするために再配置し,基本的な生物学的原理を変更しました.
  • 遺伝子発現と進化を理解するには コドン再配分を止めるメカニズムを理解することが重要です

研究 の 目的:

  • 前述のトライパノソマチドのストップコドンの再割り当てのメカニズムを調査する.
  • ストップコドンを感知コドンとして使用できる特定の遺伝的および分子的適応を特定する.
  • これらのメカニズムの進化的保存と普遍性を研究する.

主な方法:

  • Blastocrithidia nonstopの7,259のタンパク質をコードする遺伝子のインフレームストップコドンの分析
  • 新型tRNA (tRNAGlu,tRNATrp) の識別と特徴付けは,コドン再配分に関与しています.
  • 異なる種 (B.nonstop,Trypanosoma brucei,Saccharomyces cerevisiae) でのtRNA変異の設計と発現について,その機能を研究する.
  • 解放因子1の変異分析 B. 絶え間なく

主要な成果:

  • インフレームストップコドンは,B.ノンストップの高度に発現した遺伝子で不足している.UAAは唯一の終末コドンである.
  • UAGとUAAのコードンの再割り当ては,新しい同類型tRNAGluを伴う.
  • UGAの再配分は,短縮された (4塩基対) tRNATrpCCAのアンチコドン幹を通じて発生し,トリプトファンの組み込みを可能にしました.
  • エンジニアリングされた 4-bp tRNATrpの変種は,複数の種で読み込みが増加しました.
  • B. ノンストップの変異性放出因子1は,UGAの認識を特に制限し,再割り当てを強化しました.

結論:

  • Blastocrithidia nonstopは,tRNAアンチコドン幹の縮小を通じてUGAのコドン再割り当てを停止するユニークなメカニズムを使用しています.
  • 変更された解放因子1は,UGAの再割り当てをさらに強化します.
  • tRNAの改変と放出因子の変化を含む同様の戦略は,コンディロストーマ・マグナムのような他の真核生物によって採用されている.
  • これまでに知られていなかった,コドン再配分を止めるための普遍的なメカニズムが,関係のない真核生物で特定されました.