31 relations. Definition of cytochrome b6f complex in the Definitions.net dictionary. Then an electron is ejected from P680 and P700, is transferred through electron carriers and reduces P700 and NADP+, respectively (Lawlor, 2001; Taiz and Zeiger, 2010). Cytochrome B6F Complex: Un complexe protéique qui inclut les cytochromes B6 et cytochrome F. C'est retrouvé dans la membrane THYLAKOID et joue un rôle important en cours de la photosynthèse en transférant les électrons de PLASTOQUINONE à PLASTOCYANIN ou cytochrome C6.Le transfert d'électrons est accroché au transport de protons à travers la membrane. These fatty acids are released to the endoplasmic reticulum for chain elongation and desaturation (Chi et al., 2008). Due to a spatial separation of PS I and II, intermediate electron carrier molecules, i.e. As in vascular plants, in high light-stressed cells of Chlamydomonas the formation of zeaxanthin due to increased VDE activity correlates with an enhanced thermal dissipation of singlet chlorophyll in the light-harvesting antennae (Niyogi et al., 1997b), and zeaxanthin has also been implicated in the scavenging of reactive oxygen species (Baroli et al., 2003). It has been shown that nonspecific adsorption of lipids is about 100 to 200 times lower than the specific adsorption of detergent. One exception is the CP43 core antenna of PS II: its rate of synthesis does not depend on the presence of other PS II subunits, even if it is less stable in strains showing compromised PS II assembly. On a timescale of femto- to picoseconds, excited xanthophylls in the light-harvesting complexes transfer energy to chlorophylls, probably from both the S2- and the S1-excited states (Walla et al., 2002), but they also protect the photosynthetic apparatus by quenching triplet chlorophyll in the range of nanoseconds (Peterman et al., 1995, 1997). In contrast, it remains to be determined whether small chloroplast-encoded subunits participate in CES cascades because being poorly resolved by SDS-PAGE, their actual rates of translation are difficult to assess by pulse-labeling experiments with assembly-defective strains. The eyespot, which appears to be attached to the inner plastid envelope membrane, consists of β-carotene–containing lipid globules (Ohad et al., 1969; Schmidt et al., 2006) that are organized in two layers. The equation for the light-independent reaction is as follows: This biosynthetic process, which converts CO2 to energy-rich compounds powered by the energy generated by cleavage of the P-bond of ATP, is called CO2 fixation. Accordingly, they use the Gro3P pathway to generate glycerolipids using glycerol 3-phosphate. 2A, B) that consists of eight trans-membrane polypeptide subunits. Noncyclic phosphorylation can produce both ATP and NADPH with photosystems I and II. These three pathways differ not only in their protein specificities but also from an energetic point of view. The cytochrome b6f complex (plastoquinol—plastocyanin reductase) 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. Other glycerolipids, such as phosphatidyl choline, phosphatidylinositol, phosphatidylethanolamine, diphosphatidylglycerol (cardiolipin), and phosphatidylserine, are not found in cyanobacteria (Wada and Murata, 1998). Yuan Li, Gary J. Loake, in Plant Transcription Factors, 2016. Photosynth Res. The plastoquinol-cytochrome c 553 /plastocyanin oxidoreductase (Cyt b 6 f complex) catalyzes the rate limiting, quinol-oxidation step in oxygenic photosynthesis. The complex also contains a Rieske iron–sulfur protein (FeSR), in which two Fe atoms are bridged by two S atoms (Berry et al., 2000). Since crystallization experiments are generally performed at low LPRs, weak lipid adsorption may have some effects. It is known that some nucleus-encoded subunits of the three major photosynthetic complexes (the PS II and PS I reaction centers and the cytochrome b6f complex) are translocated into the lumen via the so called “ΔpH-dependent Tat pathway” (reviewed in Cline and Henry, 1996), after entering the stroma via the outer (TOC) and inner (TIC) membrane translocon complexes (reviewed in Reumann and Keegstra, 1999). The major source of ROS under such circumstances is catalyzed by respiratory burst oxidase homologs (RBOHs; Figure 24.2), analogous to the enzymes found in mammalian phagocytes (Grant and Loake, 2000; Lambeth, 2004). Copyright © 2021 Elsevier B.V. or its licensors or contributors. Andrei V. Astashkin, in Methods in Enzymology, 2015. (2009) as a demonstration of application of their just introduced five-pulse RIDME sequence. These observations define a “CES cascade,” where PsaB is required for sustained expression of PsaA, which, in turn, is required for significant production of PSAC (Wostrikoff et al., 2004). DG, diacylglycerol; SQDG, sulfoquinovosyldiacylglycerol; ACP, acyl carrier protein; CDP-DG, PGP, phosphatidylglycerolphosphate; PG, phosphatidylglycerol; DGDG, digalactosyldiacylglycerol; MGDG, monogalactosyldiacylgycerol. Metabolic consumption of H+: Proton ions from photosystem II move to the lumen via the thylakoid membrane and play an important role as electron donors in photosystem I (Hervas et al., 2003). Le complexe cytochrome b6f est un dimère dont chaque monomère est composé de huit sous-unités , à savoir quatre grosses sous-unités : PS I mutants defective for PsaB expression show no detectable synthesis of the CES subunit PsaA, whether failure to synthesize PsaB results from mutations in the chloroplast psaB gene itself (Girard-Bascou et al., 1987) or in the TAB1 or TAB2 nuclear genes, whose products are specifically required for the translation of psaB mRNA (Stampacchia et al., 1997; Dauvillée et al., 2003). The de novo fatty acid synthesis in eukaryotic microalgae strongly resembles that in cyanobacteria due to their endosymbiosis. Electrons are transferred through centers A and B to ferredoxin (Fd), a small, water-soluble Fe–S protein. The complex functions as a dimer (By similarity). It plays a major role in generating a protein gradient during photosynthesis. Hydrophobic absorption removes the detergent from the protein solution, thus promoting the incorporation of the protein into lipid bilayers to form 2-D crystals. Interacts with PGRL1A. Organic energy molecules (ATP and NADPH) from the light-dependent reaction are consumed by the synthesis of glucose from carbon dioxide in the Calvin cycle. plastoquinone (PQ) and plastocyanin (PC), are required for delivery of electrons to PS I (Allen and Forsberg, 2001). Lipid composition and metabolism in cyanobacteria differ from those in bacteria and plants. These major glycerolipids contain only hexadecanoate, octadecanoate, and their polyunsaturated fatty acids because phosphatidic acid, which is a precursor of glycerolipids in cyanobacteria, consists of hexadecanoate (C16:0) and octadecanoate (C18:0). Giovanni Finazzi, ... Fabrice Rappaport, in The Chlamydomonas Sourcebook, 2009. MGDG is produced from diacylglycerol by stereochemical isomerization at the C-4 atom of the glucose unit. Supramolecular complexes involved in photosynthesis are photosystem I (PSI), photosystem II (PSII), cytochrome b6f complex (Cit b6f) and ATP synthase complex. The latter suggestion was inferred from both in vitro and in vivo studies of the antioxidant activity of astaxanthin and its esters (Kobayashi et al., 1997a; Kobayashi and Sakamoto, 1999). This reaction occurs through the Q cycle as in Complex III. Electron transfer through Cytb6f is coupled with photon pumping into the thylakoid to produce a transthylakoid proton motive force to drive the synthesis of ATP (Sierla et al., 2013; Figure 24.1). 276: 9770 – 9774. Plant RBOHs are located on the plasma membrane and synthesize ROS into the apoplast. In mammals, three isoforms of NO synthase (NOS) have been characterized (nNOS, eNOS, and iNOS; Alderton et al., 2001). The cytochrome b 6 f complex is closely analogous to complex III in oxidative phosphorylation. Cytochrome f is a subunit of the cytochrome b6f complex that plays a role in photosynthesis by transferring electrons between photosystems II and I in plants, green algae, and cyanobacteria. Figure 2. 22:46. Playing a regulatory role in cyclic electron flow (CEF) around PSI, PGR5 contributes indirectly to PSI protection by enhancing photosynthetic control, which is a pH-dependent down-regulation of electron transfer at the cytochrome b6f complex (b6f). The heavily pigmented and highly refractive globules modulate the light intensity impinging on the photosensory rhodopsins in the adjacent plasma membrane by reflection or absorbance of light depending on its angle of incidence (Kateriya et al., 2004, see also see Volume 3, Chapter 13). This interpretation invokes an entropic role for the ΔpH, consistent with indications that a ΔpH is required for the assembly of the Tat translocase in isolated thylakoids (Mori and Cline, 2002). Identifiant d'origine: D045346; CUI UMLS: C0056934; Concept(s) lié(s) au record. Review of the function of cytomchrome b6f complex and Photosystem I in photosynthesis Additionally, the hydrogenase in the thylakoid membrane functions as an electron valve to maintain redox stability under the overloaded electron transfer caused by excess light energy (Appel et al., 2000). Le cytochrome b6 et la sous-unité IV sont semblables au cytochrome b, tandis que les protéines de Rieske des deux complexes sont homologues[5]. Cytochrome b6f Complex "Cytochrome b6f Complex" is a descriptor in the National Library of Medicine's controlled vocabulary thesaurus, MeSH (Medical Subject Headings) . The complex functions as a dimer. In a similar way, psaA mutants show reduced synthesis of the CES subunit PsaC (Takahashi et al., 1991), while PsaB and PsaA are synthesized at wild-type rates – but rapidly degraded – in psaC deletion strains (Takahashi et al., 1991). The photosynthetic electron flow between photosystems generates a H+ proton gradient across the thylakoid membranes. Information and translations of cytochrome b6f complex in the most comprehensive dictionary definitions resource on the web. The dipolar contribution was separated by dividing the RIDME traces recorded at different TR(2) values by that with TR1=5μs, and mostly manifested itself as a “bump” at t = 0 and with a half-with of ~ 15 ns. Ferguson, in Comprehensive Biophysics, 2012. The plant genome contains 10 RBOH genes (RBOHA–RBOHJ; Torres and Dangl, 2005). Structure of the cytochrome b6f complex: new prosthetic groups, Q-space, and the ‘hors d'oeuvres hypothesis’ for assembly of the complex. The membrane-embedded CF0 portion of the ATP synthase is a selective proton channel that comprises subunits I, II, III, and IV, assembled in a 1:1:(13–14):1 stoichiometry (Seelert et al., 2003; Meyer zu Tittingdorf et al., 2004). 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