Conserved in situ arrangement of complex I and III^sub 2^ in mitochondrial respiratory chain supercomplexes of mammals, yeast, and plants

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 115; no. 12; p. 3024
• Main Authors: Davies, Karen M, Blum, Thorsten B, Kühlbrandt, Werner
• Format: Journal Article
• Language: English
• Published: Washington National Academy of Sciences 20-03-2018
• Subjects: Asparagus; Assemblies; Carbonic anhydrase; Chains; Electron transfer; Electron transport chain; Fungi; Mammals; Mitochondria; Principal components analysis; Proteins; Stoichiometry; Tomography; Yarrowia lipolytica; Yeast
• ISSN: 0027-8424; 1091-6490

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 ∼4 nm resolution. Principal component analysis indicated that ∼60% of complex I formed a supercomplex with dimeric complex III, while ∼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 ∼4.5-nm globular protein density was observed on the matrix side of the complex I membrane arm, which we assign to γ-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.