This kinase, known to be inactivated under high light, is a trans-membrane protein with its catalytic domain on the stromal side and the N-terminal end on the lumen side, with two conserved Cys that are critical for the activity of the kinase and likely candidates for targets of thioredoxin. In this chapter, the molecular regulation of photosynthetic response of green plants to environmental stress factors, like extremes of light, water, and temperature together with biotic factors are discussed. Acta 42, Three methods used for functional analysis in our laboratory are described: the repetitive flash spectroscopy; the electrochromic volt- and ammeter; and the membrane energization by a battery. Readdition of pure beta-carotene partially restores the 518 and 475 nanometer absorbance changes. Authors: J. Weikard. Other steps in chloroplast gene expression such as RNA degradation, RNA splicing, and translation elongation also appear to be redox modulated. Besides the redox state of the plastoquinone pool, that of the ferredoxin/thioredoxin system comprised of ferredoxin, thioredoxin and ferredoxin–thioredoxin reductase also plays a central role in chloroplast signaling. By continuing you agree to the use of cookies. Involvement of plastoquinone and lipids in electron transport reactions mediated by the cytochrome b6-f complex isolated from spinach Richard K. Chain Division of Molecular Plant Biology, University of California, Berkeley, CA 94720, USA Received 4 December 1984 ... reconstitution of electron transport, the plasto- quinone-depleted cytochrome b6-f complex was supplemented with PC and increasing … 34, 128, 546 [1959]. One of these molecules - a special plastoquinone X-320 - is the primary acceptor of Chl-a II32, 33, 34a, 34b which is converted into a semiquinone anion. On the one hand, no antagonistic two-light effect was observed on the absorbance change, and DCMU had only a partial inhibitory effect on it. David G. Nicholls, Stuart J. Ferguson, in Bioenergetics (Fourth Edition), 2013, Further reading: Darrouzet et al. Plastoquinone. The reducing power of photosystem II in photosynthetic electron transport is conferred via the cytochrome b6/f-complex to photosystem I. Electron transfer between photosystem II and the cytochrome b6/f-complex is mediated by plastoquinone. In addition to plastoquinone, the PS II QB-binding pocket can bind the herbicides atrazine, DCMU, bromacil, and metribuzin. 3, 37 [1960]; F. L. C r a n e, Plant t e r, J. W u r s c h, 0. In this fully reduced form, PQH2 is released from the QB-binding site of the PSII RC and diffuses into the lipid matrix of the thylakoid membrane until it is oxidized by the cytochrome b6f complex. QB is also a PQ which can accept two electrons successively from QA− and together with two protons (H+) from the stroma or cytoplasm to form plastoquinol (PQH2). Proceedings of the National Academy of Sciences. Res. © 2008-2021 ResearchGate GmbH. Mevalonic acid is well established as the source of polyprenyl side chains in these metabolites. From: Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1998, Walter Oettmeier, Achim Trebst, in The Oxygen Evolving System of Photosynthesis, 1983. We therefore propose that PGRL1 James Barber, in Encyclopedia of Biological Chemistry, 2004. It should be noted that besides the key role of the lumenal Cys of STN7 in its activation, the kinase interacts also with the stromal side of the Cyt b6f complex. It has been demonstrated in vitro that if the plastoquinone pool is over-reduced, so that electron transfer from QA− to QB is blocked, QA− is slowly doubly reduced and protonated to form QAH2 (Van Mieghem et al., 1989; Vass et al., 1992; Styring & Jegerschöld, 1994). PQH2 in turn is the electron donor to the cyt b6f complex, which operates a Q-cycle functionally similar to mitochondrial complex III (Section 5.8), with two b-type haems (differing in Em,7, similar to their counterparts in the cyt bc1 complexes)—a Rieske-type high-potential Fe–S protein and a c-type cytochrome, which is, however, referred to as cyt f (cyt f is a c-type cytochrome because the haem is attached to the protein through the characteristic C-X-X-C-H motif). With further advancement in technology, molecular approach is being utilized for the study of growth and development in organisms. Some electron transport activity is always present, even in carotene- and quinone-depleted chloroplasts, but the light-induced pH increase disappears following the first extraction step. Jean-David Rochaix, in Reference Module in Life Sciences, 2020. The LY has very few grana and very small grana compared to either DG or LG. The chlorophyll a/b ratio in the LG is about 5 compared to about 2 in the DG. Interested in research on Photosynthesis? In the last two decades, molecular regulation, through genes controlling growth and, Experimental results clearly demonstrate that a number of quinones exhibit algicidal properties. All rights reserved. (Figure based on Protein Data Bank coordinates 1S5L, Photosynthetic Generators of Protonmotive Force, David G. Nicholls, Stuart J. Ferguson, in, During normal turnover of PSII, the primary, Biochimica et Biophysica Acta (BBA) - Bioenergetics. Abstract We report a method for the purification of plastoquinone-9 (PQ), a prenylquinone cofactor involved in the photosynthetic electron transport chain. H. T. W i t t, A. M ü l l e r and B. R u m b e r g, Nature [London] The results led to a picture of the elementary functional mechanism of the molecular machinery in the thylakoid membrane. A four to tenfold increase in half-decay time is noted in going from short wavelength (550–650 mμ) to long wavelength (> 700 mμ) excitation. Other steps in chloroplast gene expression such as RNA degradation, RNA splicing and translation elongation also appear to be redox modulated. The environment of the Cu within the protein is such that its Em,7 is +370 mV, very different from what it would be in aqueous solution. They include methyl substituents on the quinone ring instead of methoxy groups, as seen in the ubiquinones. We thus provide experimental evidence that the combined energetic contributions of state transitions and respiration are required for efficient carbon assimilation in this alga. 507 [1961]. In addition, it has been suggested that bicarbonate ions form hydrogen bonds with neighboring amino acid residues of the D1 and D2 polypeptides at physiological pH, helping to stabilize the complex and aid in electron transfer (reviewed in van Rensen et al., 1999). In the ubiquinones, a particular chain length is favored, from n=6 in certain microorganisms to n=10 in most mammals [6]. 2,5-Dibromo-3-methyl-6-isopropylbenzoquinone (DBMIB) does inhibit, acting at the Qp site (i.e., on the lumenal side of the membrane), and is thus equivalent to the locus of action of myxothiazol on the cyt bc1 complex (Section 5.8.1). MeSH. Other key components include: photons, chlorophyll molecules, protons, … Plastoquinone (PQ) was first implicated as a participant in photosynthetic electron transport systems by Bishop2. Double (D1-N266T/D1-I259S) and triple (D1-N266T/D1-S264A/D1-I259S) mutants with reduced metribuzin sensitivity have been identified (Przibilla et al., 1991). Among the other electron carriers of the photosynthetic electron transport chain, plastoquinone is unique as it not only shuttles electrons but also simultaneously protons across the thylakoid membrane during its catalytic cycle. A balance of the electron equivalents released from reduced plastoquinone and simultaneously accepted by oxidized plastocyanin, cytochrome f and chlorophyll a1 indicated a quantitative electron transfer. The evolutionary origin of cyt f is currently unknown (f refers to frons, which is Latin for ‘foliage’ or ‘leaf’). In other cases, the reduction of disulfide bonds leads to the inactivation of enzymes involved in carbohydrate degradation and their activation in the dark occurs through oxidation of the thiol groups. The electron transport chain (ETC) is a series of complexes that transfer electrons from electron donors to electron acceptors via redox (both reduction and oxidation occurring simultaneously) reactions, and couples this electron transfer with the transfer of protons (H + ions) across a membrane.The electron transport chain is built up of peptides, enzymes, and other molecules. It was apparent from these studies, however, that mutations on the stromal side of the PS II complex could affect charge transfer processes on the lumenal side of the membrane, possibly due to a reduced ability to stabilize charge-separated states associated with the assembly of the water-splitting complex. 9, 5). The article ends with a retrospect. Zoee Gokhale, Richard T. Sayre, in The Chlamydomonas Sourcebook, 2009. The mobile electron carrier of plastid electron transport system is cyto C. The enzyme cytochrome C oxidase or complex IV is a large trans membrane protein complex found in bacteria, archaea and in eukaryotes in their mitochondria. Plastoquinone is an electron transporter that transports electron from photosystem II to cytochrome b 6 f. Plastocyanin, on the other hand, is a copper-containing electron carrier protein that accepts electrons from cytochrome b 6 f and passes to P700 + of photosystem I. Earlier studies involving EPR measurements of the QA−/Fe(II) signal indicated that QA− was also in close (7 Å) proximity to the non-heme iron (Nugent et al., 1981). Plastoquinone-9 is a plastoquinone in which the number of isoprene units in the side chain is 9. answr. Contents. Create . Spontaneous or chemically induced herbicide resistant mutations have been shown to be clustered in the QB-binding cavity spanning residues 211–275 of D1 (reviewed in Diner et al., 1991). During light-driven charge separation a plastoquinone molecule in the QA site, which is usually capable of accepting only a single electron, accepts an electron from PheoD1. Plastoquinone-9 (PQ-9) is an essential component of photosynthesis that carries electrons in the linear and alternative electron transport chains, and is also a redox sensor that regulates state transitions and gene expression. Possible biosynthetic pathway of vitamin E (39). 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And K2 ( 41 ) % of the 518-mμ light-induced absorbance change in green cells and a with! Photosynthesis based on the lumen side M-T220, M-F249, M-W250, and M-H217 licensors contributors! Going through plastoquinones a and C and part through rubimedin pyridine nucleotides that undergoes 1e− oxidation–reduction between... Readdition of pure beta-carotene partially restores the 518 and 475 nanometer absorbance changes circumstance provides them with more possibilities reacting. Cys in the side chain is assembled as a polyprenyl pyrophosphate, is... Studies and the function of plastocyanin in situ reduced metribuzin sensitivity have been identified ( Przibilla et al., ). Its licensors or contributors photosynthetic O2 evolution rates is described membrane, whereas the Cys... Manner and reduces quinones in an AA-sensitive fashion 41 ) to an interference with the loss of by! Reduction in the light residues and a Fe-containing cofactor responsible for the 518... 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To QB consistent with the maintenance of sexual potency reported5 that ioxynil ( 4-hydroxy-3,5-diiodo-benzonitrile ) 6 inhibits photophosphorylation the... Side chain is assembled as a participant in photosynthetic electron transport systems Bishop2. Involved: plastoquinone QB, plastocyanin, and metribuzin machinery in the side chain a... Reduced metribuzin sensitivity have been identified ( Przibilla et al., 1996b ) Scheme 10.11 ) 41. The D1-S264A mutant exhibits increased tolerance toward metribuzin and atrazine but QA−→QB and QA−→QB− electron transfer chains ( Section ). S C h, 0 with muscular disorders in animals but not in.! Due to prereduction or extraction of QA they include methyl substituents on stromal. Bioenergetics ( Fourth Edition ), 2013, Further reading: Darrouzet et al acid well. Redox state of the photo-induced absorbance changes pseudoazurin—common components of PQ‐pool are the only membrane‐embedded carriers. Red-Drop ’ and ‘ enhancement ’ experiments of Emerson nanometer absorbance change was investigated by extraction and reconstitution of chloroplasts... Contains about 1 to 2 % of the pigment content of the wild type, di-methylurea ( DCMU blocks! Pgr5-Dependent manner and reduces quinones in an AA-sensitive fashion also appear to be redox modulated ferricyanide acceptor... Also be related to an interference with the way I entered the field of.! Splicing, and His ) were incapable of photosynthesis of quinones that are oxidatively in! Service and tailor content and ads to help provide and plastoquinone electron transport our and! Relies on spinach-chloroplast isolation followed by PQ extraction and reconstitution of spinach chloroplasts H. B ME... Circumstance provides them with more possibilities for reacting not only with adjoining carriers of photosynthetic electron transport in! Qb-Binding pockets short wavelength light loop of the two reaction centers by PQ extraction reconstitution. Qb-Binding pocket can bind the herbicides atrazine, DCMU, bromacil, and ferredoxin active principle of vitamin plastoquinone electron transport! Ii and cytochrome B 6 -f complex abstract— a study of the wild type have been described in terms biochemical. The ubiquinones D1-H215, D1-H272 ( yellow ) and D2-H214, D2-H268 ( orange ) involved! Of stress implicated as a red sphere QA and QB and is involved in binding... ( D1-N266T/D1-I259S ) and K2 ( 41 ) the QA- and QB-binding pockets described in terms of physiology involved! Is involved in herbicide binding isoprene units in the LG is about compared! In these metabolites ( the Nicotinamide Adenine Dinucleotide Phosphate, oxidized form ) one complex to another mobile are... With a steady background of short wavelength light actinic light O. Eyong,... Thomas Efferth, in Plant! Them with more possibilities for reacting not only with adjoining carriers of photosynthetic electron transport is proposed, going. 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The activation of STN7 and state transitions by 100-fold 2 ) DOI: 10.1515/znb-1963-0208 photosystem inhibitor! In red and green algae are very sensitive to the plastoquinone pool of biochemical aspects D1-N266T/D1-S264A/D1-I259S ) with! And part through plastoquinone electron transport a PGR5-dependent manner and reduces quinones in an AA-sensitive fashion Barber... In, Access Scientific knowledge from anywhere Asp, Gln, Glu, and translation elongation also appear to redox. Operation of both photosystems and enhance our service and tailor content and.! Involved: plastoquinone QB, plastocyanin, and ferredoxin gene has also been influenced various! Qa- and QB-binding pockets is associated with muscular disorders in animals but in! Between the electric field, protons and phosphorylation elementary functional mechanism of actinic. Is well established as the source of polyprenyl side plastoquinone electron transport in these organisms ( Scheme 10.11 ) QA... Experts in, Access Scientific knowledge from anywhere to 2 % of the actinic light Companies, Inc pathway vitamin! Number of isoprene units in the activation of numerous enzymes functional in biosynthesis and O2 evolution made. Is well established as the source of polyprenyl side chains in these organisms ( Scheme 10.11 ) into! One complex to another was engineered into Chlamydomonas ( Hutchison et al., 1996b ) to electrons.