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Author Spotlight: Unveiling Mitochondrial Contact Sites and Architectural Insights
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Biochemical Characterization of the Num1-Mdm36 Complex at the Mitochondria-Plasma Membrane Contact Site

Jongdae Won1, Yuri Choi1, Yaejin Yun1

  • 1Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 08826, Korea.

Molecules and Cells
|April 8, 2021
PubMed

Insights

The Num1-Mdm36 complex forms a heterotetramer, crucial for tethering mitochondria to the plasma membrane in yeast. This interaction is vital for mitochondrial fission and membrane contact site regulation.

Area of Science:

  • Cell biology
  • Molecular and structural biology
  • Biochemistry

Background:

  • Mitochondria-plasma membrane contact sites (MECA) are essential for cellular functions.
  • The Num1-Mdm36 complex is a key component of MECA, mediating mitochondrial tethering.
  • Understanding the Num1-Mdm36 complex's structure and stoichiometry is crucial for elucidating MECA function.

Purpose of the Study:

  • To biochemically characterize the Num1-Mdm36 complex.
  • To determine the oligomeric state and stoichiometry of the Num1-Mdm36 complex.
  • To identify the specific binding regions and affinity between Num1 and Mdm36.

Main Methods:

  • Protein purification of Num1 domains and Mdm36.
  • Chemical crosslinking to assess oligomeric states.
  • Size-exclusion chromatography coupled with multi-angle light scattering (SEC-MALS).
  • Isothermal titration calorimetry (ITC) for binding affinity.

Main Results:

  • Mdm36 exists as a dimer.
  • The Num1-Mdm36 complex forms a heterotetramer with a 2:2 stoichiometry.
  • Specific Num1 binding regions essential for Mdm36 interaction were identified.
  • Strong binding affinity demonstrated, sufficient for membrane tethering.

Conclusions:

  • The Num1-Mdm36 complex forms a stable heterotetramer at a 2:2 ratio.
  • This complex plays a critical role in tethering mitochondria to the plasma membrane.
  • Biochemical data supports a stoichiometric model for the Num1-Mdm36 complex at MECA in yeast.
Keywords:
Mdm36Num1mitochondriaplasma membranetethering

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