関連する実験動画
Updated: May 30, 2026
10:37
Toeprinting Analysis of Translation Initiation Complex Formation on Mammalian mRNAs
Published on: May 10, 2018
リボソームアセンブリファクターは,40Sアセンブリ中間体による早期の翻訳開始を防止します
Bethany S Strunk1, Cherisse R Loucks, Min Su
1Chemical Biology Doctoral Program, University of Michigan, Ann Arbor, MI 48109, USA.
Science (New York, N.Y.)
|August 13, 2011
まとめ
研究者は,リボソーム組立の重要なステップを視覚化するために,冷凍電子顕微鏡を用いた. 彼らは,未成熟の40Sリボソームサブユニットがタンパク質合成を開始するのを防ぐ7つの遅発のアセンブリファクター (AF) を特定しました.
科学分野:
- 分子生物学は分子生物学である.
- 構造生物学 構造生物学とは
- 細胞生物学 細胞生物学
背景:
- ユカリオットリボソームの生体生成には200以上のアセンブリファクター (AF) と複雑で秩序のあるステップが含まれています.
- リボソームの組み立ては核の中で始まり,成熟したサブユニットを持つサイトプラズマで終了します.
- AFの正確な役割を理解することは,翻訳制御と細胞機能を理解するために不可欠です.
研究 の 目的:
- 後期サイトプラズマ40Sリボソーム組立中間体の構造を決定する.
- この中間体上の遅結合組立因子 (AF) の位置をマップする.
- これらのAFが早期に翻訳を開始するのを防ぐメカニズムを解明する.
主な方法:
- 高解像度構造分析を達成するために電子冷凍顕微鏡 (cryo-EM) を利用しました.
- 特定のAF減退を伴うプレリボソーム複合体の生成された冷凍-EM再構築.
- 7つの主要なAFの拘束場所と空間配置を定義しました.
主要な成果:
- 後期サイトプラズマ的40S組立中間物の冷凍-EM構造は,18アングストームの解像度で解明されました.
- すべての7つの遅い結合AFの位置が正確にマッピングされました.
- これらのAFは,因子結合,mRNAチャネル,およびサブユニット結合を含む,翻訳開始のための重要なサイトを集団的にブロックします.
結論:
- 後期結合AFは重要なチェックポイントとして機能し,未成熟の40Sサブユニットが翻訳経路に入るのを防ぐ.
- 余剰抑制メカニズムは,完全に組み立てられ,機能するリボソームのみがタンパク質合成に関与することを保証します.
- この構造的洞察は,リボソーム生体生成の品質管理のための分子基盤を提供します.
関連する概念動画
02:07Improving Translational Accuracy
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...
02:33Initiation of Translation
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...
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...
02:33Initiation of Translation
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...
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...
02:53Ribosomal RNA Synthesis
Ribosome synthesis is a highly complex and coordinated process involving more than 200 assembly factors. The synthesis and processing of ribosomal components occurs not only in the nucleolus but also in the nucleoplasm and the cytoplasm of eukaryotic cells.
Ribosome biogenesis begins with the synthesis of 5S and 45S pre-rRNAs by distinct RNA polymerases. The primary transcripts are extensively processed and modified before they are bound and folded by ribosomal proteins and assembly factors,...
Ribosome biogenesis begins with the synthesis of 5S and 45S pre-rRNAs by distinct RNA polymerases. The primary transcripts are extensively processed and modified before they are bound and folded by ribosomal proteins and assembly factors,...
02:53Ribosomal RNA Synthesis
Ribosome synthesis is a highly complex and coordinated process involving more than 200 assembly factors. The synthesis and processing of ribosomal components occurs not only in the nucleolus but also in the nucleoplasm and the cytoplasm of eukaryotic cells.
Ribosome biogenesis begins with the synthesis of 5S and 45S pre-rRNAs by distinct RNA polymerases. The primary transcripts are extensively processed and modified before they are bound and folded by ribosomal proteins and assembly factors,...
Ribosome biogenesis begins with the synthesis of 5S and 45S pre-rRNAs by distinct RNA polymerases. The primary transcripts are extensively processed and modified before they are bound and folded by ribosomal proteins and assembly factors,...
01:44Termination of Translation
The large ribosomal subunit has several important structures essential to translation. These include the peptidyl transferase center (PTC) - which is the site where the peptide bond is formed - and a large, internal, water-filled tube through which the nascent polypeptide moves. This latter structure is called the Peptide Exit Tunnel, and it begins at the PTC and spans the body of the large ribosomal subunit. During translation, as the nascent polypeptide chain is synthesized, it passes through...