6QA9

Isolated complex I class refinement from Ovine respiratory supercomplex I+III2

This is a non-PDB format compatible entry.

Summary for 6QA9

• Entry DOI: 10.2210/pdb6qa9/pdb
• Related: 6Q9B 6Q9D 6Q9E
• EMDB information: 4479 4480 4481 4482
• Descriptor: NADH dehydrogenase [ubiquinone] flavoprotein 1, mitochondrial, NADH:ubiquinone oxidoreductase subunit S4, NADH:ubiquinone oxidoreductase subunit A9, ... (53 entities in total)
• Functional Keywords: complex i, cellular respiration, mitochondria, electron transport
• Biological source: Ovis aries (Sheep); More
• Total number of polymer chains: 45
• Total formula weight: 979744.28

Authors

Letts, J.A.,Sazanov, L.A. (deposition date: 2018-12-19, release date: 2019-08-21, Last modification date: 2024-10-16)

Primary citation

Letts, J.A.,Fiedorczuk, K.,Degliesposti, G.,Skehel, M.,Sazanov, L.A.
Structures of Respiratory Supercomplex I+III2Reveal Functional and Conformational Crosstalk.
Mol.Cell, 75:1131-1146.e6, 2019

PubMed Abstract: 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+III limits complex (C)I turnover, arguing against channeling. The SC structure, resolved at up to 3.8 Å in four distinct states, suggests that CoQ oxidation may be rate limiting because of unequal access of CoQ to the active sites of CIII. 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 CIII, demonstrating crosstalk between the enzymes. CoQ was identified at only three of the four binding sites in CIII, suggesting that interaction with CI disrupts CIII symmetry in a functionally relevant manner. Together, these observations indicate a more nuanced functional role for the SCs.

PubMed: 31492636
DOI: 10.1016/j.molcel.2019.07.022

Experimental method

ELECTRON MICROSCOPY (4.1 Å)