トレオニル-tRNA合成酵素におけるトランスファーRNA媒介編集. 二重差別問題に対するクラスIIの解決策
A Dock-Bregeon1, R Sankaranarayanan, P Romby
1UPR 9004 Biologie Structurale IGBMC, CNRS/INSERM/ULP BP163 67404 Cedex, Illkirch, France.
Cell
|January 4, 2001
まとめ
トレオニル-tRNA合成酵素は,特定のN末端部位で水解により,誤って結合されたセリンを編集する. この編集メカニズムは,他の合成酵素のクラスを反映し,保存されたtRNAのコンフォメーションスイッチングを精度のために強調します.
科学分野:
- 分子生物学は分子生物学である.
- 酵素学 酵素学とは
- 構造生物学 構造生物学とは
背景:
- トレオニル-tRNA合成酵素 (ThrRS) は,タンパク質合成に不可欠なクラスII合成酵素である.
- tRNAの正確なアミノアシライゼーションは不可欠であり,バリンのような類似のアミノ酸を区別する必要があります.
- 以前の研究では,ThrRSが差別のためにユニークな亜鉛イオンを使用していることが示されました.
研究 の 目的:
- 非同類アミノ酸,特にセリンに対するThrRSの差別メカニズムを調査する.
- 誤電したtRNAの編集におけるN端末ドメインの役割を明らかにする.
- クラスIとクラスIIの合成酵素の編集メカニズムを比較する.
主な方法:
- セリルアデニラートアナログを用いたThrRSの結晶構造分析.
- アミノアシレーションと水解を研究するための生化学分析.
- tRNA編集メカニズムの比較分析.
主要な成果:
- 結晶構造は,セリンが活性化段階で完全に区別できないことを明らかにしました.
- 誤電されたser-tRNA (Thr) の水解は,ThrRS.のN端領域内の異なった部位で発生する.
- 両方の合成酵素のクラスは,アミノアシレーションと編集のためにtRNA CCAのエンドコンフォメーションスイッチングを使用しています.
結論:
- ThrRSは,誤電したser-tRNAを水解するために特定のN端末編集部を使用しています.
- クラスIとクラスIIの合成酵素の編集機構は,tRNA結合とアミノ酸活性化と一致する鏡像として提案されています.
- 保存されたtRNA CCAの末端構造の柔軟性は,合成酵素のクラス全体で正確なアミノアシレーションと編集を支えている.
関連する概念動画
01:23RNA Structure
Overview
The basic structure of RNA consists of a five-carbon sugar and one of four nitrogenous bases. Although most RNA is single-stranded, it can form complex secondary and tertiary structures. Such structures play essential roles in the regulation of transcription and translation.
Different Types of RNA Have the Same Basic Structure
There are three main types of ribonucleic acid (RNA): messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). All three RNA types consist of a...
The basic structure of RNA consists of a five-carbon sugar and one of four nitrogenous bases. Although most RNA is single-stranded, it can form complex secondary and tertiary structures. Such structures play essential roles in the regulation of transcription and translation.
Different Types of RNA Have the Same Basic Structure
There are three main types of ribonucleic acid (RNA): messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). All three RNA types consist of a...
02:36Transfer RNA Synthesis
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...
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...
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...
02:42Transcription Attenuation in Prokaryotes
Transcriptional attenuation occurs when RNA transcription is prematurely terminated due to the formation of a terminator mRNA hairpin structure. Bacteria use these hairpins to regulate the transcription process and control the synthesis of several amino acids including histidine, lysine, threonine, and phenylalanine. Transcription attenuation takes place in the non-coding regions of mRNA.
There are several different mechanisms used to attenuate transcription. In ribosome mediated...
There are several different mechanisms used to attenuate transcription. In ribosome mediated...
01:19RNA Structure
The basic structure of RNA consists of a string of ribonucleotides attached by phosphodiester bonds. Although most RNA is single-stranded, it can form complex secondary and tertiary structures. Such structures play essential roles in the regulation of transcription and translation.
Different Types of RNA Have the Same Basic Structure
There are three main types of ribonucleic acid (RNA) involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). All three...
Different Types of RNA Have the Same Basic Structure
There are three main types of ribonucleic acid (RNA) involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). All three...
02:36Transfer RNA Synthesis
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...
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...