4pv1

Cytochrome B6F structure from M. laminosus with the quinone analog inhibitor stigmatellin

spinqualitylabelsall models 4pv1, resolution 3.00Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4pv1 is a 8 chain structure with sequence from Mastigocladus laminosus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 3Å Ligands: 7PH, 8K6, BCR, CD, CLA, FES, HEC, MYS, OPC, SMA, SQD, UMQ Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function CYB6_MASLA Component of the cytochrome b6-f complex, which mediates electron transfer between photosystem II (PSII) and photosystem I (PSI), cyclic electron flow around PSI, and state transitions.[HAMAP-Rule:MF_00633] Publication Abstract from PubMed The cytochrome bc complexes b6f and bc1 catalyze proton-coupled quinol/quinone redox reactions to generate a transmembrane proton electrochemical gradient. Quinol oxidation on the electrochemically positive (p) interface of the complex occurs at the end of a narrow quinol/quinone entry/exit Qp portal, 11 A long in bc complexes. Superoxide, which has multiple signaling functions, is a by-product of the p-side quinol oxidation. Although the transmembrane core and the chemistry of quinone redox reactions are conserved in bc complexes, the rate of superoxide generation is an order of magnitude greater in the b6f complex, implying that functionally significant differences in structure exist between the b6f and bc1 complexes on the p-side. A unique structure feature of the b6f p-side quinol oxidation site is the presence of a single chlorophyll-a molecule whose function is unrelated to light harvesting. This study describes a cocrystal structure of the cytochrome b6f complex with the quinol analog stigmatellin, which partitions in the Qp portal of the bc1 complex, but not effectively in b6f. It is inferred that the Qp portal is partially occluded in the b6f complex relative to bc1. Based on a discrete molecular-dynamics analysis, occlusion of the Qp portal is attributed to the presence of the chlorophyll phytyl tail, which increases the quinone residence time within the Qp portal and is inferred to be a cause of enhanced superoxide production. This study attributes a novel (to our knowledge), structure-linked function to the otherwise enigmatic chlorophyll-a in the b6f complex, which may also be relevant to intracellular redox signaling. Traffic within the cytochrome b6f lipoprotein complex: gating of the quinone portal.,Hasan SS, Proctor EA, Yamashita E, Dokholyan NV, Cramer WA Biophys J. 2014 Oct 7;107(7):1620-8. doi: 10.1016/j.bpj.2014.08.003. PMID:25296314 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Cytochrome b6

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