2025-10-06 理化学研究所,岡山大学,日本原子力研究開発機構,総合科学研究機構
図1 ラットチオレドキシンの変異周辺および活性中心付近の結晶構造
野生型(左)およびF54L変異型(右)のラットチオレドキシンの結晶構造(変異周辺および活性中心を含む一部)。野生型ではF54は周辺のアミノ酸残基と疎水性相互作用を形成しているが、変異型ではそれらの相互作用は消失している。またF54/F54Lからヘリックスを介して活性中心が配置している。C:システイン、F:フェニルアラニン、L:ロイシン、V:バリン(いずれもアミノ酸)。
<関連情報>
- https://www.riken.jp/press/2025/20251006_1/index.html
- https://www.sciencedirect.com/science/article/pii/S0304416525001059
チオレドキシンのF54L変異は、タンパク質の不安定性と触媒中心の変動の増加を示す The F54L mutation of Thioredoxin shows protein instability and increased fluctuations of the catalytic center
Takumi Baba, Go Ueno, Chika Ohe, Shuku Saji, Sachiko Yamamoto, Masaki Yamamoto, Hiroshi Nakagawa, Nobuo Okazaki, Mamoru Ouchida, Iori Kawasaki Ohmori, Kohei Takeshita
Biochimica et Biophysica Acta (BBA) – General Subjects Available online: 13 September 2025
DOI:https://doi.org/10.1016/j.bbagen.2025.130860
Highlights
- Trx-F54L shows reduced disulfide reductase activity and thermal stability.
- Crystal structure reveals disrupted hydrophobic interactions around F54.
- The F54L mutation increases flexibility near the catalytic C32–C35 motif.
- Catalytic site deformation may underlie functional impairment of Trx-F54L.
- The molecular defects of Trx-F54L may underlie its pathological role.
Abstract
Thioredoxin is a ubiquitous redox protein that acts as an electron donor via its conserved dithiol motif (C32GPC35), catalyzing dithiol–disulfide exchange to regulate the redox state of target proteins. It supports antioxidant defense via peroxiredoxins, facilitates DNA synthesis by donating electrons to ribonucleotide reductase, and regulates redox-sensitive signaling pathways, including those controlling transcription and apoptosis. Neuronal degeneration and chronic kidney disease have been observed in Txn-F54L mutant rats; however, the details of why the Txn mutation causes these phenomena remain unknown. The present study aimed to elucidate the functional and structural changes caused by the F54L mutation. The Thioredoxin-F54L showed less insulin-reducing activity and more thermosensitivity to denaturation in the body temperature range compared to the wild type. The crystal structure revealed that F54 forms hydrophobic interactions with the surrounding hydrophobic amino acids. In addition, molecular dynamics simulation predicts increased fluctuations around the F54L mutation and a tendency for the distance between residues C32 and C35 at the catalytic center to be widened. The increased distance between residues C32 and C35 of the catalytic center may affect the reducing activity of the enzyme on the substrate. The finding that Thioredoxin-F54L is prone to denaturation at normal body temperature may reduce the normally functioning Thioredoxin. These molecular characteristics of Thioredoxin-F54L may be related to brain and kidney disease development in the Txn-F54L rats.
