関連する実験動画
Updated: Sep 9, 2025

06:06
In Vitro Analysis of E3 Ubiquitin Ligase Function
Published on: May 14, 2021
5.4K
ユカリオットタンパク質品質管理の中心となる巨大なE4リガゼであるUBR4複合体の構造
Daniel B Grabarczyk1, Julian F Ehrmann1,2, Paul Murphy1
1Research Institute of Molecular Pathology, Vienna BioCenter (VBC), Vienna, Austria.
まとめ
研究者らはUBR4 E4リガゼメガ複合体の構造を明らかにし,有毒なタンパク質の集積物を排除するために決定的な役割を果たしました. この複合体は 損傷したタンパク質を分解し 細胞の健康と機能を維持します
科学分野:
- 細胞生物学
- タンパク質の分解の分子機構
- ウビキチン-プロテアソーム系
背景:
- ユーカリ細胞は有害なタンパク質を除去する品質管理システムを持っています.
- Ubiquitin-proteasomeシステム (UPS) は,誤った折り畳みまたは損傷したタンパク質を分解するために不可欠です.
- UBR4はUPS内の重要なE4ユビキチンリガゼとして機能し,分解信号を強化します.
研究 の 目的:
- UBR4 E4 リガゼ複合体の構造構造を解明する.
- UBR4が集積傾向のあるタンパク質を標的と ubiquitinatesするメカニズムを理解する.
- 基質認識とユビキチネーションにおけるUBR4コファクター,KCMF1,CALM1の役割を特定する.
主な方法:
- UBR4-KCMF1-CALM1メガコンプレクスの高解像度構造を決定するために,冷凍電子顕微鏡 (冷凍EM) が使用されました.
- 基質結合とユビキチン鎖の延長を分析するために生化学的測定法を使用した.
- 構造分析は,基板結合部位と触媒ユニット組織を特定することに焦点を当てました.
主要な成果:
- UBR4 E4リガゼメガコンプレックスの大規模な1.3メガダルトンのリング構造が解明されました.
- 構造は,基板結合と柔軟に関連付けられた触媒モジュールのための中央領域を明らかにしました.
- UBR4は基板と結合し,プロテアソーム分解に不可欠なライシン-48結合ユビキチン鎖を拡張することが示された.
- KCMF1は,プレビキチネーションとN-デグロンに基づく効率的なターゲティングを保証する重要な基板フィルターとして特定されました.
結論:
- UBR4 E4リガゼは,真核タンパク質の品質管理に不可欠な,大きく保存されたメガコンプレックスを形成する.
- 構造的な洞察は,UBR4が欠陥タンパク質の効率的なクリアリングのためにユビキチネーションを拡大する方法を説明します.
- UBR4アーキテクチャの種特有の適応は,多様な細胞文脈で正確な規制を可能にします.
関連する概念動画
Protein Folding Quality Check in the RER
3.8K
ER is the primary site for the maturation and folding of soluble and transmembrane secretory proteins. The calnexin cycle is a specific chaperone system that folds and assesses the confirmation of N-glycosylated proteins before they can exit the ER lumen. The primary players of this quality check pipeline are the lectins, ER-resident chaperones, and a glucosyl transferase enzyme. In case the calnexin system in the lumen fails to salvage a misfolded protein, it is transported to the cytoplasm...
3.8K
The Unfolded Protein Response
5.1K
The ER is the hub of protein synthesis in a cell. It has robust systems to quality control protein folding and also for degradation of terminally misfolded proteins. Under normal conditions, a small proportion of misfolded proteins that cannot be salvaged need to be transported to the cytoplasm by the ER-associated degradation or ERAD pathways. However, if the ERAD cannot handle the misfolded proteins, the cell activates the unfolded protein response or UPR to adjust the protein folding...
5.1K
Protein Complexes with Interchangeable Parts
2.6K
Groups of proteins may form a complex where each protein in this complex has a different role in the overall execution of the complex’s function. Often some of the proteins in the complex can be replaced by a closely related variant to give a complex that contains many of the same components yet is functionally distinct.
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order...
The SCF ubiquitin ligase is a protein complex of five individual proteins. This complex attaches ubiquitin to other target proteins to mark them for degradation. In order...
2.6K
Regulated Protein Degradation
7.6K
It is vital to regulate the activity of enzymatic as well as non-enzymatic proteins inside the cell. This can be achieved either through creating a balance between their rate of synthesis and degradation or regulating the intrinsic activity of the protein. Both these regulation mechanisms play an essential role in the normal functioning of cells.
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
Protein degradation plays two important roles in the cells. It helps to protect cells from misfolded or damaged proteins before they lead to a...
7.6K
Regulation of the Unfolded Protein Response
2.6K
Inositol-requiring kinase one or IRE1 is the most conserved eukaryotic unfolded protein response (UPR) receptor. It is a type I transmembrane protein kinase receptor with a distinctive site-specific RNase activity. As the binding mechanics of the misfolded proteins with the N-terminal domain of IRE-1 are unclear, three binding models — direct, indirect, and allosteric -- are proposed for receptor activation. Nevertheless, it is known that once a misfolded protein associates with IRE1, it...
2.6K
The Proteasome
9.0K
Eukaryotic cells can degrade proteins through several pathways. One of the most important amongst these is the ubiquitin-proteasome pathway. It helps the cell eliminate the misfolded, damaged, or unwarranted cytoplasmic proteins in a highly specific manner.
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
9.0K

