適応的な制約の直接的な実証
Stephen P Miller1, Mark Lunzer, Antony M Dean
1BioTechnology Institute, University of Minnesota, St. Paul, MN 55108, USA.
Science (New York, N.Y.)
|October 21, 2006
まとめ
ベータ-イソプロピルマラート脱水素酶 (IMDH) の誘導進化は,コファクター阻害のような酵素の制約が適応的進化を形作ることを明らかにしています. これらの制限は,エンジニアリングされた酵素がニコチナミドアデニンジヌクレオチドリン酸塩 (NADP) に対してより低い親和性を進化させる理由を説明します.
科学分野:
- バイオケミストリー バイオケミストリー
- 進化生物学の進化生物学について
- 酵素工学とは
背景:
- 適応の形成における進化的制約の役割は,まだ完全に理解されていない.
- ベータ-イソプロピルマラート脱水素酵素 (IMDH) は自然にニコチナミドアデニン・ディヌクレオチド (NAD) を使用しますが,ニコチナミドアデニン・ディヌクレオチド・リン酸塩 (NADP) の特異性のために設計することができます.
- 酵素の進化を理解するには,適応的な風景と固有の制限を調査する必要があります.
研究 の 目的:
- エンジニアリングされたIMDHの適応進化に対する酵素制約の影響を調査する.
- 観察された進化的結果が,理論的適応的景観からの予測と一致するかどうかを判断する.
- 酵素進化における選択と制約の相互作用を解明する.
主な方法:
- 誘導進化は,エンジニアリングされたIMDHの共同酵素特異性をNADからNADPに変更するために使用されました.
- NADPとNADPHに対する変異酵素の親和性を測定した.
- 観察された進化の軌道は,既知の酵素制約を組み込んだモデルに対して分析されました.
主要な成果:
- エンジニアリングされたIMDHは,NADPに対するより低い親和性を一貫して進化させ,NADP抑制の減少に対する選択に対する相関反応である.
- この結果は,最大回転率 (kcat),NADP/NADPH親和関係,およびNAD/NADP使用トレードオフによって制限される適応的な環境と一致しています.
- 高細胞内NADPHレベルとタンパク質合成コストは,NADの使用をさらに強化しました.
結論:
- 進化的制約は,適応的進化の方向と結果に大きな影響を与えます.
- 酵素の限界によって定義される適応的な風景は,酵素の進化を理解するために極めて重要です.
- 選択的圧力は固有の制約と相互作用し,予測可能な進化パターンを生み出します.
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