Journal
MOLECULAR CELL
Volume 75, Issue 6, Pages 1131-+Publisher
CELL PRESS
DOI: 10.1016/j.molcel.2019.07.022
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Funding
- European Union (EU) [701309]
- MRC [MC_U105184326] Funding Source: UKRI
- Marie Curie Actions (MSCA) [701309] Funding Source: Marie Curie Actions (MSCA)
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The mitochondrial electron transport chain complexes are organized into supercomplexes (SCs) of defined stoichiometry, which have been proposed to regulate electron flux via substrate channeling. We demonstrate that CoQ trapping in the isolated SC I+III2 limits complex (C)I turnover, arguing against channeling. The SC structure, resolved at up to 3.8 angstrom in four distinct states, suggests that CoQ oxidation may be rate limiting because of unequal access of CoQ to the active sites of CIII2. CI shows a transition between closed and open conformations, accompanied by the striking rotation of a key transmembrane helix. Furthermore, the state of CI affects the conformational flexibility within CIII2, demonstrating crosstalk between the enzymes. CoQ was identified at only three of the four binding sites in CIII2, suggesting that interaction with CI disrupts CIII2 symmetry in a functionally relevant manner. Together, these observations indicate a more nuanced functional role for the SCs.
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