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6qc2

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Ovine respiratory supercomplex I+III2 open class 2

6qc2, resolution 4.20Å

Structural highlights

6qc2 is a 11 chain structure with sequence from Ovis aries. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Method:	Electron Microscopy, Resolution 4.2Å
Ligands:
Experimental data:	Check to display Experimental Data
Resources:	FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

NU3M_SHEEP Core subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I) that is believed to belong to the minimal assembly required for catalysis. Complex I functions in the transfer of electrons from NADH to the respiratory chain. The immediate electron acceptor for the enzyme is believed to be ubiquinone (By similarity).

Publication Abstract from PubMed

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 A 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.

Structures of Respiratory Supercomplex I+III2 Reveal Functional and Conformational Crosstalk.,Letts JA, Fiedorczuk K, Degliesposti G, Skehel M, Sazanov LA Mol Cell. 2019 Sep 19;75(6):1131-1146.e6. doi: 10.1016/j.molcel.2019.07.022. Epub, 2019 Sep 3. PMID:31492636^[1]

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

References

↑ Letts JA, Fiedorczuk K, Degliesposti G, Skehel M, Sazanov LA. Structures of Respiratory Supercomplex I+III2 Reveal Functional and Conformational Crosstalk. Mol Cell. 2019 Sep 19;75(6):1131-1146.e6. doi: 10.1016/j.molcel.2019.07.022. Epub, 2019 Sep 3. PMID:31492636 doi:http://dx.doi.org/10.1016/j.molcel.2019.07.022