The structure of MgtE in the absence of magnesium provides new insights into channel gating

PLoS Biol. 2021 Apr 27;19(4):e3001231. doi: 10.1371/journal.pbio.3001231. eCollection 2021 Apr.

Abstract

MgtE is a Mg2+ channel conserved in organisms ranging from prokaryotes to eukaryotes, including humans, and plays an important role in Mg2+ homeostasis. The previously determined MgtE structures in the Mg2+-bound, closed-state, and structure-based functional analyses of MgtE revealed that the binding of Mg2+ ions to the MgtE cytoplasmic domain induces channel inactivation to maintain Mg2+ homeostasis. There are no structures of the transmembrane (TM) domain for MgtE in Mg2+-free conditions, and the pore-opening mechanism has thus remained unclear. Here, we determined the cryo-electron microscopy (cryo-EM) structure of the MgtE-Fab complex in the absence of Mg2+ ions. The Mg2+-free MgtE TM domain structure and its comparison with the Mg2+-bound, closed-state structure, together with functional analyses, showed the Mg2+-dependent pore opening of MgtE on the cytoplasmic side and revealed the kink motions of the TM2 and TM5 helices at the glycine residues, which are important for channel activity. Overall, our work provides structure-based mechanistic insights into the channel gating of MgtE.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antiporters / chemistry*
  • Antiporters / metabolism
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / metabolism
  • Binding Sites / drug effects
  • Biological Transport
  • Cryoelectron Microscopy
  • Crystallography, X-Ray
  • Cytoplasm / metabolism
  • Ion Channel Gating / drug effects
  • Ion Channel Gating / physiology*
  • Kinetics
  • Magnesium / metabolism
  • Magnesium / pharmacology
  • Models, Molecular
  • Protein Domains / drug effects
  • Protein Domains / physiology
  • Protein Structure, Quaternary
  • Protein Structure, Secondary
  • Thermus thermophilus / metabolism

Substances

  • Antiporters
  • Bacterial Proteins
  • MgtE protein, bacteria
  • Magnesium

Grants and funding

This work was supported by funding from the Ministry of Science and Technology of China (National Key R&D Program of China: 2016YFA0502800) to M.H.; funding from the National Natural Science Foundation of China (32071234) to M.H., the Innovative Research Team of High-level Local Universities in Shanghai and a key laboratory program of the Education Commission of Shanghai Municipality (ZDSYS14005); grants from Basis for Supporting Innovative Drug Discovery and Life Science Research (BINDS) from the Japan Agency of Medical Research and Development (AMED) (grant no. 19am0101079; Support No. 0451); Research on Development of New Drugs from the AMED; and Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (JSPS) (nos. 18K05334 and 19H00923). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.