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Publication Abstract from PubMed

The enzymes of the mitochondrial electron transport chain are key players of cell metabolism. Despite being active when isolated, in vivo they associate into supercomplexes(1), whose precise role is debated. Supercomplexes CIII(2)CIV(1-2) (refs. (2,3)), CICIII(2) (ref. (4)) and CICIII(2)CIV (respirasome)(5-10) exist in mammals, but in contrast to CICIII(2) and the respirasome, to date the only known eukaryotic structures of CIII(2)CIV(1-2) come from Saccharomyces cerevisiae(11,12) and plants(13), which have different organization. Here we present the first, to our knowledge, structures of mammalian (mouse and ovine) CIII(2)CIV and its assembly intermediates, in different conformations. We describe the assembly of CIII(2)CIV from the CIII(2) precursor to the final CIII(2)CIV conformation, driven by the insertion of the N terminus of the assembly factor SCAF1 (ref. (14)) deep into CIII(2), while its C terminus is integrated into CIV. Our structures (which include CICIII(2) and the respirasome) also confirm that SCAF1 is exclusively required for the assembly of CIII(2)CIV and has no role in the assembly of the respirasome. We show that CIII(2) is asymmetric due to the presence of only one copy of subunit 9, which straddles both monomers and prevents the attachment of a second copy of SCAF1 to CIII(2), explaining the presence of one copy of CIV in CIII(2)CIV in mammals. Finally, we show that CIII(2) and CIV gain catalytic advantage when assembled into the supercomplex and propose a role for CIII(2)CIV in fine tuning the efficiency of electron transfer in the electron transport chain.

Structure and assembly of the mammalian mitochondrial supercomplex CIII(2)CIV.,Vercellino I, Sazanov LA Nature. 2021 Oct;598(7880):364-367. doi: 10.1038/s41586-021-03927-z. Epub 2021 , Oct 6. PMID:34616041^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.