Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 115, Issue 12, Pages 3024-3029Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1720702115
Keywords
respirasomes; respiratory chain supercomplexes; cryo-electron tomography; subtomogram averaging; mitochondria
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Funding
- Max Planck Society
- Cluster of Excellence Frankfurt Macromolecular Complexes - Deutsche Forschungsgemeinschaft
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We used electron cryo-tomography and subtomogram averaging to investigate the structure of complex I and its supramolecular assemblies in the inner mitochondrial membrane of mammals, fungi, and plants. Tomographic volumes containing complex I were averaged at similar to 4 nmresolution. Principal component analysis indicated that similar to 60% of complex I formed a supercomplex with dimeric complex III, while similar to 40% were not associated with other respiratory chain complexes. The mutual arrangement of complex I and III2 was essentially conserved in all supercomplexes investigated. In addition, up to two copies of monomeric complex IV were associated with the complex I1III2 assembly in bovine heart and the yeast Yarrowia lipolytica, but their positions varied. No complex IV was detected in the respiratory supercomplex of the plant Asparagus officinalis. Instead, an similar to 4.5-nm globular protein density was observed on the matrix side of the complex I membrane arm, which we assign to gamma-carbonic anhydrase. Our results demonstrate that respiratory chain supercomplexes in situ have a conserved core of complex I and III2, but otherwise their stoichiometry and structure varies. The conserved features of supercomplex assemblies indicate an important role in respiratory electron transfer.
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