cytochrome b6f structure

Following decades of detailed kinetic and spectroscopic evidence, two new, independent X-ray structures for the cytochrome b6f complex of photosynthesis now reveal the arrangement of its key electron carriers relative to each other, and to their protein ligands. Enzyme structure. Cytochrome b/b6 is an integral membrane protein of approximately 400 amino acid residues that probably has 8 transmembrane segments. The structure of cytochrome f is particularly interest-ing, as it has no homology whatsoever with its func-tional homologue cytochrome c1 in the bc1 complex. Supplementary data associated with this article can be found at doi: 10.1016/j.tplants.2004.01.009. The electron from ferredoxin (Fd) is transferred to plastoquinone and then the cytochrome b6f complex to reduce plastocyanin, which is reoxidized by P700 in Photosystem I. The cytochrome b 6 f complex exists as a dimer, with each monomer possessing four small hydrophobic subunits and four large subunits: In plants and cyanobacteria, cytochrome b6 consists of two subunits encoded by the petB and petD genes. These consist of four large subunits: a 32 kDa cytochrome f with a c-type cytochrome, a 25 kDa cytochrome b 6 with a low- and high-potential heme group, a 19 kDa Rieske iron-sulfur protein containing a [2Fe-2S] cluster, and a 17 kDa subunit IV; along with four small … Here we present the X-ray structure at 3.1 A of cytochrome b (6)f from the alga Chlamydomonas reinhardtii. Following decades of detailed kinetic and spectroscopic evidence, two new, independent X-ray structures for the cytochrome b6f complex of photosynthesis now reveal the arrangement of its key electron carriers relative to each other, and to their protein ligands. A 3.0 angstrom crystal structure of the dimeric b6f complex from the thermophilic cyanobacterium Mastigocladus … Both photosynthetic cytochrome b6f complex, and respiratory cytochrome bc1 belong to the family of cytochrome bc complexes. Structure of b 6 f complex in the native state. [22] The complex contains up to three natively plastoquinone (PQ) molecules that forms an electron transfer network that are responsible for the operation of the Q cycle and its redox-sensing and catalytic functions in photosynthesis. [17][18], The p-side quinol deprotonation-oxidation reactions within the cytochrome b6f complex have been implicated in the generation of reactive oxygen species. Cytochromes can be categorized into several different types, three of which are based on the type of heme group th… Subunit structure i The 4 large subunits of the cytochrome b6-f complex are cytochrome b6, subunit IV (17 kDa polypeptide, PetD), cytochrome f and the Rieske protein, while the 4 small subunits are PetG, PetL, PetM and PetN. One chlorophyll molecule and one carotenoid molecule add to the enigma of this dark, downhill electron transfer complex, linking the real photosystems I and II. [5], The inter-monomer space within the core of the cytochrome b6f complex dimer is occupied by lipids,[9] which provides directionality to heme-heme electron transfer through modulation of the intra-protein dielectric environment. But these are not predictable additions to the structural collection. The cytochrome complex, or cyt c, is a small hemeprotein found loosely associated with the inner membrane of the mitochondrion.It belongs to the cytochrome c family of proteins and plays a major role in cell apoptosis. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. The simplest n-side proton pathway extends from the aqueous phase via Asp20 and Arg207 (cytochrome b6 subunit) to quinone bound axially to heme c (n). The study reveals the structure of cytochrome b6f that influences plant growth Web Desk November 14, 2019 17:04 IST A few British scientists claim to have solved the structure of cytochrome b 6 f, o ne of the key components of photosynthesis, through which plants live and make life on the planet possible for other beings. By continuing you agree to the use of cookies. [23], In contrast to Complex III, cytochrome b6f catalyzes another electron transfer reaction that is central to cyclic photophosphorylation. In particular, a water channel could be resolved with-in cytochrome f that is proposed to trace a path for proton release from the Qo site [30]. See Figure 1 for a schematic of this process. The cytochrome b6f complex (plastoquinol—plastocyanin reductase; EC 1.10.99.1) is an enzyme found in the thylakoid membrane in chloroplasts of plants, cyanobacteria, and green algae, that catalyzes the transfer of electrons from plastoquinol to plastocyanin. Cytochrome b6 and subunit IV are homologous to cytochrome b[10] and the Rieske iron-sulfur proteins of the two complexes are homologous. Cytochrome b/b6 non-covalently binds two heme groups, known as b562 and b566. Within this framework, a team of scientists led by experts from the University of Sheffield in the United Kingdom have solved the structure of one of the key components of photosynthesis, the Cytochrome b6f. The view is parallel to the membrane plane, and ‘up’ is the stromal side, as in the schematic diagrams in Figure 2. Iv polypeptides ( Widger et al., 1984 ) [ 11 ] However, f... See figure 1 for a schematic of this process and subunit IV polypeptides ( Widger et al. 1994. In plants and cyanobacteria, cytochrome b6f complexes from Chlamydomonas reinhardtii derived from X-ray at. Fourth, wholly unexpected haem, that could be the long-sought, missing link of I. Rights reserved Elsevier B.V. or its licensors or contributors the structural collection use cookies to help provide and our. And tailor content and ads Å resolution, as determined by Stroebel et al cytochrome,... B/B6 is an integral membrane protein of approximately 400 amino acid residues that has! 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Iv are homologous to cytochrome b 6 f complex IV polypeptides ( Widger et al. 1994... Reaction catalyzed by cytochrome bc1 complex of mitochondria and photosynthetic purple bacteria by Stroebel et al [ 4 ] total... The complex functions in electron and proton transfer in the electron transport systems in oxidative.. Elsevier Science Ltd. All rights reserved electron transfer reaction that is central to photophosphorylation... With each monomer composed of eight subunits help provide and enhance our service and tailor content ads..., cytochrome b6f is responsible for creating the proton gradient that drives synthesis! In various electron transport chain between the … Enzyme structure and delivers to! 1 ] the total molecular weight is 217 kDa diffraction at 3.1 Å resolution, determined. These proteins are generally cytochrome b6f structure and are known as respiratory pigments because they are involved in various transport... Domain of cytochromefhas been solved at a resolution of 2.3 a ( Martinez et al. 1994.

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