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Electron Transport Chain: Complex I and II01:46

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Updated: Jul 5, 2025

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Accessory subunit NDUFB4 participates in mitochondrial complex I supercomplex formation.

Gaganvir Parmar1, Claire Fong-McMaster1, Chantal A Pileggi1

  • 1Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada; Ottawa Institute of Systems Biology, University of Ottawa, Ontario, Canada.

The Journal of Biological Chemistry
|January 11, 2024
PubMed
Summary

Mitochondrial respiratory supercomplexes (SCs) are crucial for cellular energy. NDUFB4 mutations disrupt respirasome assembly, impairing mitochondrial function and metabolism, highlighting SCs

Keywords:
NDUFB4electron transport chainmitochondriaoxidative phosphorylationrespirasomesteady-state metabolomicssupercomplexes

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Area of Science:

  • Biochemistry
  • Cell Biology
  • Mitochondrial Biology

Background:

  • Respiratory supercomplexes (SCs) are supramolecular assemblies of mitochondrial electron transport chain complexes.
  • The precise role of SCs in mitochondrial respiratory function and their assembly mechanisms, particularly the I1III2IV1 respirasome, are not fully understood.
  • Dysfunction in SCs is implicated in neurodegeneration and metabolic syndromes.

Purpose of the Study:

  • To investigate the role of the NDUFB4 subunit in the assembly and function of respiratory supercomplexes.
  • To decipher the function of I1III2-containing respiratory SCs in cellular metabolism using specific NDUFB4 point mutations.
  • To minimize functional consequences to complex I assembly while studying SCs.

Main Methods:

  • Introduction of specific point mutations (N24A and R30A) in the NDUFB4 subunit.
  • Analysis of respirasome assembly and mitochondrial respiratory flux.
  • Steady-state metabolomics to assess changes in cellular metabolites.

Main Results:

  • NDUFB4 point mutations N24A and R30A significantly impaired I1III2IV1 respirasome assembly.
  • Mutations led to a reduction in mitochondrial respiratory flux.
  • Metabolomics revealed a global decrease in citric acid cycle metabolites, impacting NADH-generating substrates.

Conclusions:

  • NDUFB4 plays an integral role in the assembly of the I1III2IV1 respirasome.
  • Respiratory supercomplexes are functionally significant in regulating mammalian cell bioenergetics.
  • Disruption of SCs impacts cellular metabolism, with implications for metabolic diseases.