8bep
From Proteopedia
Cryo-EM structure of the Arabidopsis thaliana I+III2 supercomplex (CIII MPP domain)
Structural highlights
FunctionMPPA1_ARATH Substrate recognition and binding subunit of the essential mitochondrial processing protease (MPP), which cleaves the mitochondrial sequence off newly imported precursors proteins.[UniProtKB:P11914] Component of the ubiquinol-cytochrome c oxidoreductase, a multisubunit transmembrane complex that is part of the mitochondrial electron transport chain which drives oxidative phosphorylation. The respiratory chain contains 3 multisubunit complexes succinate dehydrogenase (complex II, CII), ubiquinol-cytochrome c oxidoreductase (cytochrome b-c1 complex, complex III, CIII) and cytochrome c oxidase (complex IV, CIV), that cooperate to transfer electrons derived from NADH and succinate to molecular oxygen, creating an electrochemical gradient over the inner membrane that drives transmembrane transport and the ATP synthase. The cytochrome b-c1 complex catalyzes electron transfer from ubiquinol to cytochrome c, linking this redox reaction to translocation of protons across the mitochondrial inner membrane, with protons being carried across the membrane as hydrogens on the quinol. In the process called Q cycle, 2 protons are consumed from the matrix, 4 protons are released into the intermembrane space and 2 electrons are passed to cytochrome c.[UniProtKB:P07257] Publication Abstract from PubMedProtein complexes of the mitochondrial respiratory chain assemble into respiratory supercomplexes. Here we present the high-resolution electron cryo-microscopy structure of the Arabidopsis respiratory supercomplex consisting of complex I and a complex III dimer, with a total of 68 protein subunits and numerous bound cofactors. A complex I-ferredoxin, subunit B14.7 and P9, a newly defined subunit of plant complex I, mediate supercomplex formation. The component complexes stabilize one another, enabling new detailed insights into their structure. We describe (1) an interrupted aqueous passage for proton translocation in the membrane arm of complex I; (2) a new coenzyme A within the carbonic anhydrase module of plant complex I defining a second catalytic centre; and (3) the water structure at the proton exit pathway of complex III(2) with a co-purified ubiquinone in the Q(O) site. We propose that the main role of the plant supercomplex is to stabilize its components in the membrane. Cryo-EM structure of the respiratory I + III(2) supercomplex from Arabidopsis thaliana at 2 A resolution.,Klusch N, Dreimann M, Senkler J, Rugen N, Kuhlbrandt W, Braun HP Nat Plants. 2023 Jan;9(1):142-156. doi: 10.1038/s41477-022-01308-6. Epub 2022 Dec , 30. PMID:36585502[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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