オルガノメタリックとラジカル中間物質は,ディフタミド生物合成のメカニズムを明らかにする
Min Dong1, Venkatesan Kathiresan2, Michael K Fenwick1
1Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA.
Science (New York, N.Y.)
|March 29, 2018
まとめ
ラジカルなSAM酵素は,独特の鉄-炭素結合中間体によってディフタミドを形成する. この有機金属のステップは この重要な生物合成経路における 炭素-炭素結合の形成に不可欠です
科学分野:
- 生物化学
- 酵素学
- 構造生物学
背景:
- ディフタミドは,ユカリオットと古生物の延長因子2 (EF-2) で発見された,翻訳後に改変された独特のヒスティジン残基である.
- その生物合成はタンパク質合成に不可欠ですが,その基礎となる酵素機構,特に初期的なSAM酵素触媒のステップは,まだ完全に理解されていません.
研究 の 目的:
- ディフタミド生物合成における初期炭素-炭素結合形成のメカニズムを解明する.
- ラジカルS-アデノシルメチオニン (SAM) 酵素触媒反応に関与する主要な中間物質を特定し,特徴づけること.
主な方法:
- 瞬時の中間物質を捕まえるための急速冷凍技術
- X線結晶学を含む構造生物学的な方法を用いて酵素基板複合体の分析.
- オーガノメタリックとオーガニックラジカルの中間物質の特性
主要な成果:
- 3-アミノ-3-カルボキシプロピル (ACP) ラジカルと酵素の [4Fe-4S] クラスタの間の鉄-炭素 (Fe-C) 結合を特徴とする新しい有機金属中間物質を捕獲した.
- この中間物質が基質 (EF-2) に添加されたときに有機基質に変換され,ヒスティジンにACP基質が添加されたことを示す.
- 結晶構造は,酵素の鉄-硫黄のクラスタの近くのSAM C-S結合割れ場所の正確な位置を明らかにした.
結論:
- この研究は,SAMの酵素触媒における有機金属中間物質の直接的な証拠を提供する.
- この発見は,SAM酵素による選択的なC-S結合分裂のメカニズムを説明する.
- この研究は,重要なディフタミド生物合成経路における重要なステップを明確にします.
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