Functional roles of Mg2+ binding sites in ion-dependent gating of a Mg2+ channel, MgtE, revealed by solution NMR

Tatsuro Maruyama, Shunsuke Imai, Tsukasa Kusakizako, Motoyuki Hattori, Ryuichiro Ishitani, Osamu Nureki, Koichi Ito, Andrès D. Maturana, Ichio Shimada, Masanori Osawa

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Abstract

Magnesium ions (Mg2+) are divalent cations essential for various cellular functions. Mg2+ homeostasis is maintained through Mg2+ channels such as MgtE, a prokaryotic Mg2+ channel whose gating is regulated by intracellular Mg2+ levels. Our previous crystal structure of MgtE in the Mg2+-bound, closed state revealed the existence of seven crystallographically-independent Mg2+-binding sites, Mg1–Mg7. The role of Mg2+-binding to each site in channel closure remains unknown. Here, we investigated Mg2+-dependent changes in the structure and dynamics of MgtE using nuclear magnetic resonance spectroscopy. Mg2+-titration experiments, using wild-type and mutant forms of MgtE, revealed that the Mg2+ binding sites Mg1, Mg2, Mg3, and Mg6, exhibited cooperativity and a higher affinity for Mg2+, enabling the remaining Mg2+ binding sites, Mg4, Mg5, and Mg7, to play important roles in channel closure. This study revealed the role of each Mg2+-binding site in MgtE gating, underlying the mechanism of cellular Mg2+ homeostasis.

Original languageEnglish
Article numbere31596
JournaleLife
Volume7
DOIs
Publication statusPublished - 2018 Apr 3

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Binding Sites
Nuclear magnetic resonance
Ions
Homeostasis
Divalent Cations
Titration
Magnesium
Nuclear magnetic resonance spectroscopy
Magnetic Resonance Spectroscopy
Crystal structure
Experiments

ASJC Scopus subject areas

  • Neuroscience(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Immunology and Microbiology(all)

Cite this

Functional roles of Mg2+ binding sites in ion-dependent gating of a Mg2+ channel, MgtE, revealed by solution NMR. / Maruyama, Tatsuro; Imai, Shunsuke; Kusakizako, Tsukasa; Hattori, Motoyuki; Ishitani, Ryuichiro; Nureki, Osamu; Ito, Koichi; Maturana, Andrès D.; Shimada, Ichio; Osawa, Masanori.

In: eLife, Vol. 7, e31596, 03.04.2018.

Research output: Contribution to journalArticle

Maruyama, T, Imai, S, Kusakizako, T, Hattori, M, Ishitani, R, Nureki, O, Ito, K, Maturana, AD, Shimada, I & Osawa, M 2018, 'Functional roles of Mg2+ binding sites in ion-dependent gating of a Mg2+ channel, MgtE, revealed by solution NMR', eLife, vol. 7, e31596. https://doi.org/10.7554/eLife.31596
Maruyama, Tatsuro ; Imai, Shunsuke ; Kusakizako, Tsukasa ; Hattori, Motoyuki ; Ishitani, Ryuichiro ; Nureki, Osamu ; Ito, Koichi ; Maturana, Andrès D. ; Shimada, Ichio ; Osawa, Masanori. / Functional roles of Mg2+ binding sites in ion-dependent gating of a Mg2+ channel, MgtE, revealed by solution NMR. In: eLife. 2018 ; Vol. 7.
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