Aims: Mitochondrial respiratory supercomplexes mediate redox electron transfer, generating a proton gradient for ATP synthesis. To provide structural information on the function of supercomplexes in physiologically relevant conditions, we conducted cryoelectron microscopy studies with supercomplexes in a lipid-preserving state. Results: Here, we present cryoelectron microscopy structures of bovine respiratory supercomplex I 1 III 2 IV 1 by using a lipid-preserving sample preparation. The preparation greatly enhances the intercomplex quinone transfer activity. The structures reveal large intercomplex motions that result in different shapes and sizes of the intercomplex space between complexes I and III, forming a dynamic substrate pool. Biochemical and structural analyses indicated that intercomplex phospholipids mediate the intercomplex motions. An analysis of the different classes of focus-refined complex I showed that structural switches due to quinone reduction led to the formation of a novel channel that could transfer reduced quinones to the intercomplex substrate pool. Innovation and Conclusion: Our results indicate potential mechanism for the facilitated electron transfer involving a dynamic substrate pool and intercomplex movement by which supercomplexes play an active role in the regulation of metabolic flux and reactive oxygen species.
Organizational Affiliation:
Department of Bioengineering, College of Engineering, Hanyang University, Seoul, Korea.
National Instrumentation Center for Environmental Management (NICEM), Seoul National University, Seoul, Korea.
Graduate School of Medical Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Korea.
Center for Biomolecular and Cellular Structure, Institute for Basic Science (IBS), Daejeon, Korea.
Voronoi Diagram Research Center, Hanyang University, Seoul, Korea.
Department of Bioscience and Biotechnology, Sejong University, Seoul, Korea.
School of Mechanical Engineering, College of Engineering, Hanyang University, Seoul, Korea.
Department of Convergence Medicine, Pusan National University Medical School, Gyeongsangnamdo, Korea.
Electron Microscopy Research Center, Korea Basic Science Institute (KBSI), Chungcheongbukdo, Korea.
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