29xz

Cryo-EM structure of Rhodobacter capsulatus cytochrome bc1 dimer at 2.16 A resolution with water molecules and quinone in the quinone reduction site

spinqualitylabelsall models 29xz, resolution 2.16Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 29xz is a 6 chain structure with sequence from Rhodobacter capsulatus SB 1003. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: Electron Microscopy, Resolution 2.16Å Ligands: FES, HEC, HEM, UMQ, UQ1 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function UCRI_RHOCB 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. Publication Abstract from PubMed The function of cytochrome bc(1), a widespread energy-conserving enzyme, requires the coordinated activity of two quinone-binding sites (Q(o) catalyzing oxidation of ubiquinol and Q(i) catalyzing reduction of ubiquinone). The operation of Q(o), but not Q(i), involves large-scale movement of the head domain of iron-sulfur protein (ISP-HD). How the respective sites accommodate quinone molecules for efficient catalysis remains elusive. Here, we present high-resolution cryoelectron microscopy structures of bacterial cytochrome bc(1) with native ubiquinone molecules in various states. They show that the quinone headgroup occupies a catalytically competent position in Q(o) only when the ISP-HD interacts with cytochrome b. When the ISP-HD does not interact with this subunit, quinone is present in the hydrophobic groove, however its headgroup is prevented from reaching the catalytic cavity by steric hindrance. In this state, the position of quinone headgroup is clearly not fixed. In contrast, all structures show Q(i) in the same state with a well-resolved and catalytically competent quinone headgroup, but with its tail not fixed. These distinctly different ubiquinone binding modes for Q(o) and Q(i) secure the smooth operation of cytochrome bc(1). Distinct ubiquinone binding at the oxidation and reduction sites of cytochrome bc(1).,Pietras R, Wojcik-Augustyn A, Mielecki B, Sarewicz M, Jaciuk M, Koziej L, Glatt S, Osyczka A Proc Natl Acad Sci U S A. 2026 Sep 8;123(36):e2618242123. doi: , 10.1073/pnas.2618242123. Epub 2026 Sep 1. PMID:42679026 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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