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Cryo-EM structure of a fungal mitochondrial calcium uniporter

Nam X Nguyen1,2, Jean-Paul Armache3, Changkeun Lee1,2,4

  • 1Howard Hughes Medical Institute and Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX, USA.

Nature
|July 12, 2018
PubMed

Insights

The structure of the fungal mitochondrial calcium uniporter (MCU) was determined, revealing insights into its assembly and how it selectively transports calcium ions across the inner mitochondrial membrane.

Area of Science:

  • Biochemistry
  • Structural Biology
  • Molecular Biology

Background:

  • The mitochondrial calcium uniporter (MCU) is a key regulator of cellular calcium homeostasis.
  • Understanding MCU structure is crucial for deciphering its function in calcium signaling and mitochondrial physiology.

Purpose of the Study:

  • To determine the high-resolution structure of the Neosartorya fischeri MCU (NfMCU) orthologue.
  • To elucidate the molecular mechanisms underlying MCU assembly, calcium selectivity, and inhibitor interactions.

Main Methods:

  • Phase-plate cryo-electron microscopy was employed to determine the NfMCU structure.
  • The structure was resolved to 3.8 Å resolution, enabling detailed atomic analysis.

Main Results:

  • The NfMCU forms a homotetrameric channel with a conserved overall architecture compared to human MCU.
  • The structure reveals a tetrameric ring formed by the amino-terminal domain and an ion-conducting pore domain with a selectivity filter at the TM2 helix.
  • The conserved DIME motif's sidechains are positioned within the pore, suggesting a role in calcium permeation.

Conclusions:

  • The determined NfMCU structure provides a molecular blueprint for MCU channel assembly and function.
  • Insights into the selectivity filter and DIME motif offer potential targets for therapeutic intervention in calcium-related diseases.
  • This study advances our understanding of mitochondrial calcium transport and its regulation.

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