6t0b | pdb_00006t0b
The III2-IV(5B)2 respiratory supercomplex from S. cerevisiae
Structural highlights
Function[COX1_YEAST] Cytochrome c oxidase is the component of the respiratory chain that catalyzes the reduction of oxygen to water. Subunits 1-3 form the functional core of the enzyme complex. CO I is the catalytic subunit of the enzyme. Electrons originating in cytochrome c are transferred via the copper A center of subunit 2 and heme A of subunit 1 to the bimetallic center formed by heme A3 and copper B. [COX13_YEAST] Cytochrome c oxidase is the component of the respiratory chain that catalyzes the reduction of oxygen to water. Not necessary for assembly of the enzyme complex but interacts with ATP and thereby modulates the enzyme activity. [QCR7_YEAST] Component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is part of the mitochondrial respiratory chain that generates an electrochemical potential coupled to ATP synthesis. The complex couples electron transfer from ubiquinol to cytochrome c. QCR7 is involved in redox-linked proton pumping. [QCR2_YEAST] Component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is part of the mitochondrial respiratory chain that generates an electrochemical potential coupled to ATP synthesis. The complex couples electron transfer from ubiquinol to cytochrome c. QCR2 is required for the assembly of the complex. [QCR1_YEAST] Component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is part of the mitochondrial respiratory chain that generates an electrochemical potential coupled to ATP synthesis. The complex couples electron transfer from ubiquinol to cytochrome c. COR1 may mediate formation of the complex between cytochromes c and c1. [RCF2_YEAST] Assembly factor that plays a role in the assembly of the respiratory chain supercomplexes (SCs) composed of ubiquinol-cytochrome c oxidoreductase (cytochrome b-c1 complex, complex III, CIII) and cytochrome c oxidase (complex IV, CIV). May be required for late-stage assembly of the COX12 and COX13 subunits (PubMed:22342701, PubMed:22310663). Required for the generation and maintenance of a normal proton motive force (PMF) across the inner mitochondrial membrane (IMM) by preventing proton leakage through an inactive population of CIV that accumulates when RCF1 and/or RCF2 proteins are absent (PubMed:30683696, PubMed:31591265).[1] [2] [3] [4] [COX6_YEAST] This is the heme A-containing chain of cytochrome c oxidase, the terminal oxidase in mitochondrial electron transport. [COX3_YEAST] Subunits I, II and III form the functional core of the enzyme complex. [QCR6_YEAST] Component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is part of the mitochondrial respiratory chain that generates an electrochemical potential coupled to ATP synthesis. The complex couples electron transfer from ubiquinol to cytochrome c. QCR6 may mediate formation of the complex between cytochromes c and c1. [CYB_YEAST] Component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is part of the mitochondrial respiratory chain that generates an electrochemical potential coupled to ATP synthesis. The complex couples electron transfer from ubiquinol to cytochrome c. [QCR9_YEAST] Component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is part of the mitochondrial respiratory chain that generates an electrochemical potential coupled to ATP synthesis. The complex couples electron transfer from ubiquinol to cytochrome c. QCR9 is required for formation of a fully functional complex. [COX2_YEAST] Cytochrome c oxidase is the component of the respiratory chain that catalyzes the reduction of oxygen to water. Subunits 1-3 form the functional core of the enzyme complex. Subunit 2 transfers the electrons from cytochrome c via its binuclear copper A center to the bimetallic center of the catalytic subunit 1. [COX12_YEAST] This protein is one of the nuclear-coded polypeptide chains of cytochrome c oxidase, the terminal oxidase in mitochondrial electron transport. This protein may be one of the heme-binding subunits of the oxidase. [COX5B_YEAST] Component of the cytochrome c oxidase, the last enzyme in 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. Cytochrome c oxidase is the component of the respiratory chain that catalyzes the reduction of oxygen to water. Electrons originating from reduced cytochrome c in the intermembrane space (IMS) are transferred via the dinuclear copper A center (CU(A)) of COX2 and heme A of COX1 to the active site in COX1, a binuclear center (BNC) formed by heme A3 and copper B (CU(B)). The BNC reduces molecular oxygen to 2 water molecules using 4 electrons from cytochrome c in the IMS and 4 protons from the mitochondrial matrix.[UniProtKB:P00424] [QCR8_YEAST] Component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is part of the mitochondrial respiratory chain that generates an electrochemical potential coupled to ATP synthesis. The complex couples electron transfer from ubiquinol to cytochrome c. QCR8, together with cytochrome b, binds to ubiquinone. [CY1_YEAST] Heme-containing component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is part of the mitochondrial respiratory chain that generates an electrochemical potential coupled to ATP synthesis. The complex couples electron transfer from ubiquinol to cytochrome c. [COX9_YEAST] This small integral protein plays a role in holoenzyme assembly or stability. [QCR10_YEAST] Component of the ubiquinol-cytochrome c reductase complex (complex III or cytochrome b-c1 complex), which is part of the mitochondrial respiratory chain that generates an electrochemical potential coupled to ATP synthesis. The complex couples electron transfer from ubiquinol to cytochrome c. QCR10 is required for stable association of the iron-sulfur protein with the complex. [UCRI_YEAST] 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. The complex couples electron transfer from ubiquinol to cytochrome c. Publication Abstract from PubMedThe organization of the mitochondrial electron transport chain proteins into supercomplexes (SCs) is now undisputed; however, their assembly process, or the role of differential expression isoforms, remain to be determined. In Saccharomyces cerevisiae, cytochrome c oxidase (CIV) forms SCs of varying stoichiometry with cytochrome bc 1 (CIII). Recent studies have revealed, in normoxic growth conditions, an interface made exclusively by Cox5A, the only yeast respiratory protein that exists as one of two isoforms depending on oxygen levels. Here we present the cryo-EM structures of the III2-IV1 and III2-IV2 SCs containing the hypoxic isoform Cox5B solved at 3.4 and 2.8 A, respectively. We show that the change of isoform does not affect SC formation or activity, and that SC stoichiometry is dictated by the level of CIII/CIV biosynthesis. Comparison of the CIV(5B)- and CIV(5A)-containing SC structures highlighted few differences, found mainly in the region of Cox5. Additional density was revealed in all SCs, independent of the CIV isoform, in a pocket formed by Cox1, Cox3, Cox12, and Cox13, away from the CIII-CIV interface. In the CIV(5B)-containing hypoxic SCs, this could be confidently assigned to the hypoxia-induced gene 1 (Hig1) type 2 protein Rcf2. With conserved residues in mammalian Hig1 proteins and Cox3/Cox12/Cox13 orthologs, we propose that Hig1 type 2 proteins are stoichiometric subunits of CIV, at least when within a III-IV SC. Rcf2 revealed in cryo-EM structures of hypoxic isoforms of mature mitochondrial III-IV supercomplexes.,Hartley AM, Meunier B, Pinotsis N, Marechal A Proc Natl Acad Sci U S A. 2020 Apr 14. pii: 1920612117. doi:, 10.1073/pnas.1920612117. PMID:32291341[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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