NMR リラクゼーション分散を用いたE. coli ディヒドロフォラート還元酵素からのアロステリック製品放出の構造的基礎の定義
David Oyen1, R Bryn Fenwick1, Phillip C Aoto1
1Department of Integrative Structural and Computational Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute , 10550 North Torrey Pines Road, La Jolla, California 92037, United States.
Journal of the American Chemical Society
|July 25, 2017
まとめ
ディヒドロフォラート還元酵素は,同因子NADPHが結合すると,その産物であるテトラヒドロフォラート (THF) をより速く放出する. これはNADPHが
科学分野:
- 酵素学
- 構造生物学
- 生物化学
背景:
- E. coliの二酸化葉酸還元酵素からテトラヒドロフォラート (THF) の放出は,その触媒サイクルにおける速度を制限するステップです.
- 産物放出は内在的経路 (NADPH欠席) またはアロステリック経路 (NADPH結合) で起こり,後者は解離率を著しく増加させる.
- 精密な酵素構造とTHF構成は,アロステル経路の一時的な興奮状態では特徴づけられていない.
研究 の 目的:
- ディヒドロフォラート還元酵素におけるアロステリック製品の構造的基礎を解明する.
- NADPH結合興奮状態における酵素構造とTHF構成を調査する.
主な方法:
- サイドチェーンの陽子NMRリラクゼーション分散測定
- X線結晶検査です
- 構造に基づく化学変化の予測
主要な成果:
- 興奮状態では,NADPHコファクターのニコチナミド環が一時的に活性部位に入り,THFプテリン環を移動させます.
- THFのp-アミノベンゾイル-l-グルタマートの尾は,拡張された活性部位の裂け目に緩やかに結合しています.
- NADPHによるこの改造は,THFの急速な放出を促進する,人口が少ない高エネルギー状態を生み出します.
結論:
- NADPHコファクターは,ダイヒドロフォラート還元酵素の活性部位とTHF構成を活性的に再構成する.
- 活性部位へのニコチナミド環の一時的な侵入は,アロステリック製品の急速な放出のための興奮状態の形成の鍵です.
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