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Consistent structure between bacterial and mitochondrial NADH:ubiquinone oxidoreductase (complex I)
V Guénebaut1, A Schlitt, H Weiss
1Structural Biology and Biocomputing Programme, European Molecular Biology Laboratory, Heidelberg, Germany.
Journal of Molecular Biology
|March 26, 1998
Summary
Bacterial and mitochondrial complex I share structural similarities, with mitochondrial complex I featuring additional subunits that stabilize its structure. These additions may play a role in cofactor biosynthesis.
Area of Science:
- Biochemistry
- Structural Biology
- Microbiology
Background:
- Respiratory chains in bacteria and mitochondria utilize proton-pumping NADH:ubiquinone oxidoreductase (complex I).
- Bacterial complex I has a ~530 kDa mass with 14 subunits.
- Mitochondrial complex I is larger (~1 MDa) with 14 bacterial homologues plus ~27 additional subunits.
Purpose of the Study:
- To determine the three-dimensional structures of bacterial and mitochondrial complex I.
- To compare the structural organization and identify differences between bacterial and mitochondrial complex I.
Main Methods:
- Electron microscopy of isolated complex I particles from E. coli and N. crassa.
- Random conical tilt reconstruction technique for 3D modeling.
- Negative staining for particle visualization.
Main Results:
- Both bacterial and mitochondrial complex I exhibit an L-shaped structure with membrane and peripheral arms.
- The consistent arm lengths suggest functional implications.
- Additional mitochondrial subunits are located around the arm junction and membrane arm, stabilizing the structure.
- A specific location in the peripheral arm may house subunits involved in cofactor biosynthesis.
Conclusions:
- The structural framework of prokaryotic complex I is conserved and stabilized by additional proteins in eukaryotes.
- The additional mass in mitochondrial complex I likely contributes to structural integrity and potentially specialized functions like cofactor biosynthesis.