CaiTのNa(+) 独立で協力的な基板/製品アンチポートの構造的基礎
Sabrina Schulze1, Stefan Köster, Ulrike Geldmacher
1Department of Structural Biology, Max Planck Institute of Biophysics, Max-von-Laue Strasse 3, 60438 Frankfurt am Main, Germany.
Nature
|September 11, 2010
まとめ
研究者らは,ナトリウムに依存しないカルニチン/ブチロベタインアンチポーターCaiTの構造を決定し,ナトリウムイオンに頼らずに膜を横断する溶液輸送のための新しいメカニズムを明らかにしました.
科学分野:
- 構造生物学 構造生物学とは
- メンブラン輸送は,膜輸送です.
- バイオケミストリー バイオケミストリー
背景:
- 生物膜輸送は生命にとって不可欠であり,しばしば二次輸送媒介によって媒介されます.
- ベタイン/カルニチン/コリントランスポーター (BCCT) は,通常,ナトリウム (Na+) または陽子 (H+) に依存しています.
- CaiTのナトリウムに依存しない性質は,BCCTファミリーの中でユニークなケースを示しています.
研究 の 目的:
- ナトリウムに依存しないカルニチン/ブチロベタインアンチポーター (CaiT) 機能の構造的基礎を解明する.
- Na+またはH+に依存しない状態で溶質輸送のメカニズムを理解する.
- CaiTの機能的状態と基板結合を特徴づける.
主な方法:
- X線結晶学を用いて,Proteus mirabilis (PmCaiT) とEscherichia coli (EcCaiT) からCaiTの構造を決定した.
- 機能研究のために,CaiTをプロテオリポソームに再構成した.
- 拘束性アッセイと基質の協力性の分析が行われました.
主要な成果:
- PmCaiT (2.3-A) とEcCaiT (3.5-A) の構造は,内向きの形状を示している.
- Na+イオンではなくメチオニン硫黄原子が,CaiT.の輸送部位における基板を調整する.
- EcCaiTは,2つの結合されたブチロベタイン分子,輸送部位と細胞外ポケットの1つを示し,協同結合を示した.
結論:
- CaiTは,メチオニンの調整を含む新しいナトリウムに依存しない輸送機構を使用しています.
- CaiTの構造は,交替アクセスメカニズムの完全なイメージを提供します.
- 細胞外部が調節部として作用する協力的な基板結合により,輸送効率が向上します.
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