6q9e
Complex III2 focused refinement from Ovine respiratory supercomplex I+III2
Structural highlights
Function[CYB_SHEEP] Component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is a respiratory chain that generates an electrochemical potential coupled to ATP synthesis. [W5PZC9_SHEEP] This is a component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is part of the mitochondrial respiratory chain. This protein may mediate formation of the complex between cytochromes c and c1.[PIRNR:PIRNR000019] [W5P2X9_SHEEP] Component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is a respiratory chain that generates an electrochemical potential coupled to ATP synthesis.[RuleBase:RU004494] Publication Abstract from PubMedThe 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
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