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Updated: Jul 13, 2026

Analyzing Supercomplexes of the Mitochondrial Electron Transport Chain with Native Electrophoresis, In-gel Assays, and Electroelution
08:37

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The proton-pumping respiratory complex I of bacteria and mitochondria and its homologue in chloroplasts

T Friedrich1, K Steinmüller, H Weiss

  • 1Institut für Biochemie, Heinrich-Heine-Universität Düsseldorf, Germany.

FEBS Letters
|June 26, 1995
PubMed

Insights

Complex I, essential for ATP synthesis, shares a core structure in mitochondria and bacteria. However, chloroplasts and cyanobacteria may utilize alternative electron donors for their Complex I.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Photosynthesis Research

Background:

  • Complex I (NADH:ubiquinone oxidoreductase) is crucial for generating proton motive force and ATP synthesis in cellular respiration.
  • Homologous Complex I structures are found in eukaryotic mitochondria and bacterial plasma membranes, comprising 14 core polypeptides, FMN, and iron-sulfur clusters.

Purpose of the Study:

  • To investigate the evolutionary conservation and potential variations of Complex I structure and function.
  • To explore the differences in Complex I subunits between mitochondrial/bacterial forms and those potentially present in chloroplasts and cyanobacteria.

Main Methods:

  • Comparative analysis of protein subunit composition across different organisms (eukaryotes, bacteria, plants, cyanobacteria).
  • Examination of gene content in mitochondrial, plastidial, and cyanobacterial genomes related to Complex I subunits.

Main Results:

  • A conserved core of 14 subunits exists in mitochondrial and bacterial Complex I.
  • While many core subunit genes are conserved in plant plastids and cyanobacteria, genes for the NADH dehydrogenase part are absent.
  • Mitochondrial Complex I contains accessory subunits absent in bacteria.

Conclusions:

  • Chloroplasts and cyanobacteria likely possess a Complex I with a modified electron input mechanism.
  • This alternative Complex I may function as a NAD(P)H: or ferredoxin:plastoquinone oxidoreductase, potentially involved in photosynthetic cyclic electron transport.

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