Research Abstract


Structural basis for ion selectivity revealed by high-resolution crystal structure of Mg2+ channel ​MgtE

2014年11月4日 Nature Communications 5 : 5374 doi: 10.1038/ncomms6374


竹田 弘法1,2, 服部 素之1,2,3,4, 西澤 知宏1,2, 山下 恵太郎5, Syed T. A. Shah6, Martin Caffrey6, Andrés D. Maturana7, 石谷 隆一郎1,2 & 濡木 理1,2

  1. 東京大学大学院 理学系研究科 生物科学専攻
  2. 理化学研究所 グローバル研究クラスタ
  3. 科学技術振興機構 さきがけ
  4. 復旦大学(中国)
  5. 理化学研究所 放射光科学総合研究センター 生命系放射光利用システム開発ユニット
  6. ダブリン大学 トリニティカレッジ(アイルランド)
  7. 名古屋大学大学院 生命農学研究科 生命技術科学専攻
Magnesium is the most abundant divalent cation in living cells and is crucial to several biological processes. MgtE is a Mg2+ channel distributed in all domains of life that contributes to the maintenance of cellular Mg2+ homeostasis. Here we report the high-resolution crystal structures of the transmembrane domain of MgtE, bound to Mg2+, Mn2+ and Ca2+. The high-resolution Mg2+-bound crystal structure clearly visualized the hydrated Mg2+ ion within its selectivity filter. Based on those structures and biochemical analyses, we propose a cation selectivity mechanism for MgtE in which the geometry of the hydration shell of the fully hydrated Mg2+ ion is recognized by the side-chain carboxylate groups in the selectivity filter. This is in contrast to the K+-selective filter of KcsA, which recognizes a dehydrated K+ ion. Our results further revealed a cation-binding site on the periplasmic side, which regulate channel opening and prevents conduction of near-cognate cations.