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José A. Navarro - One of the best experts on this subject based on the ideXlab platform.
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the heterologous expression of a plastocyanin in the diatom phaeodactylum tricornutum improves cell growth under iron deficient conditions
Physiologia Plantarum, 2021Co-Authors: Carmen Castell, Manuel Hervas, Jose M. Ortega, Mercedes Roncel, Pilar Bernalbayard, José A. NavarroAbstract:We have investigated if the heterologous expression of a functional green alga plastocyanin in the diatom Phaeodactylum tricornutum can improve photosynthetic activity and cell growth. Previous in vitro assays showed that a single-mutant of the plastocyanin from the green algae Chlamydomonas reinhardtii is effective in reducing P. tricornutum photosystem I. In this study, in vivo assays with P. tricornutum strains expressing this plastocyanin indicate that even the relatively low intracellular concentrations of holo-plastocyanin detected (≈4 μM) are enough to promote an increased growth (up to 60%) under iron-deficient conditions as compared with the WT strain, measured as higher cell densities, content in pigments and active photosystem I, global photosynthetic rates per cell, and even cell volume. In addition, the presence of plastocyanin as an additional photosynthetic electron carrier seems to decrease the over-reduction of the plastoquinone pool. Consequently, it promotes an improvement in the maximum quantum yield of both photosystem II and I, together with a decrease in the acceptor side photoinhibition of photosystem II-also associated to a reduced oxidative stress-a decrease in the peroxidation of membrane lipids in the choroplast, and a lower degree of limitation on the donor side of photosystem I. Thus the heterologous plastocyanin appears to act as a functional electron carrier, alternative to the native Cytochrome C6 , under iron-limiting conditions.
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iron deficiency induces a partial inhibition of the photosynthetic electron transport and a high sensitivity to light in the diatom phaeodactylum tricornutum
Frontiers in Plant Science, 2016Co-Authors: Mercedes Roncel, Manuel Hervas, José A. Navarro, Antonio A Gonzalezrodriguez, Belen Naranjo, Pilar Bernalbayard, Anna Marika Lindahl, Jose M. OrtegaAbstract:Iron limitation is the major factor controlling phytoplankton growth in vast regions of the contemporary oceans. In this study, a combination of thermoluminescence, chlorophyll fluorescence and P700 absorbance measurements have been used to elucidate the effects of iron deficiency in the photosynthetic electron transport of the marine diatom Phaeodactylum tricornutum. Thermoluminescence was used to determine the effects of iron deficiency on Photosystem II activity. Excitation of iron-replete Phaeodactylum tricornutum cells with single turn-over flashes induced the appearance of thermoluminescence glow curves with two components with different peaks of temperature and contributions to the total signal intensity: the B band (23 oC, 63%), and the AG band (40 oC, 37%). Iron limitation did not significantly alter these bands, but induced a decrease of the total thermoluminescence signal. Far red excitation did not increase the amount of the AG band in iron-limited cells, as observed for iron-replete cells. The effect of iron deficiency on the photosystem I activity was also examined by measuring the changes in P700 redox state during illumination. The electron donation to photosystem I was substantially reduced in iron-deficient cells. This could be related with the important decline on Cytochrome C6 content observed in these cells. Iron deficiency also induced a marked increase in light sensitivity in Phaeodactylum tricornutum cells. A drastic increase in the level of peroxidation of chloroplast lipids was detected in iron-deficient cells even when grown under standard conditions at low light intensity. Illumination with a light intensity of 300 E m-2 s-1 during different time periods caused a dramatic disappearance in thermoluminescence signal in cells grown under low iron concentration, this treatment not affecting to the signal in iron-replete cells. The results of this work suggest that iron deficiency induces partial blocking of the electron transfer between photosystem II and photosystem I, due to a lower concentration of the electron donor Cytochrome C6. This decreased electron transfer may induce the over-reduction of the plastoquinone pool and consequently the appearance of acceptor side photoinhibition in photosystem II even at low light intensities. The functionality of chlororespiratory electron transfer pathway under iron restricted conditions is also discussed
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redox properties of arabidopsis Cytochrome C6 are independent of the loop extension specific to higher plants
Biochimica et Biophysica Acta, 2004Co-Authors: Jurgen Wastl, Manuel Hervas, José A. Navarro, Miguel A. Rosa, Fernando P Molinaheredia, Derek S Bendall, Christopher J HoweAbstract:Cytochrome C6 (cytC6) from Arabidopsis differs from the cyanobacterial and algal homologues in several redox properties. It is possible that these differences might be due to the presence of a 12 amino acid residue loop extension common to higher plant cytC6 proteins. However, homology modelling suggests this is not the case. We report experiments to test if differences in biochemical properties could be due to this extension. Analysis of mutant forms of Arabidopsis cytC6 in which the entire extension was lacking, or a pair of cysteine residues in the extension had been exchanged for serine, revealed no significant effect of these changes on either the redox potential of the haem group or the reactivity towards Photosystem I (PSI). We conclude that the differences in properties are due to more subtle unidentified differences in structure, and that the sequence extension in the higher plant proteins has a function yet to be identified.
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the efficient functioning of photosynthesis and respiration in synechocystis sp pcc 6803 strictly requires the presence of either Cytochrome C6 or plastocyanin
Journal of Biological Chemistry, 2004Co-Authors: Raul V Duran, Manuel Hervas, Miguel A. Rosa, José A. NavarroAbstract:In cyanobacteria, Cytochrome C6 and plastocyanin are able to replace each other as redox carriers in the photosynthetic and respiratory electron transport chains with the synthesis of one or another protein being regulated by the copper concentration in the culture medium. However, the presence of a third unidentified electron carrier has been suggested. To address this point, we have constructed two deletion mutants of the cyanobacterium Synechocystis sp. PCC 6803, each variant lacking either the petE or petJ gene, which respectively codes for the copper or heme protein. The photoautotrophic and heterotrophic growth rate of the two mutants in copper-free and copper-supplemented medium as well as their photosystem I reduction kinetics in vivo were compared with those of wild-type cells. The two mutant strains grow at equivalent rates and show similar in vivo photosystem I reduction kinetics as wild-type cells when cultured in media that allow the expression of just one of the two electron donor proteins, but their ability to grow and reduce photosystem I is much lower when neither Cytochrome C6 nor plastocyanin is expressed. These findings indicate that the normal functioning of the cyanobacterial photosynthetic and respiratory chains obligatorily depends on the presence of either Cytochrome C6 or plastocyanin.
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a comparative structural and functional analysis of cyanobacterial plastocyanin and Cytochrome c 6 as alternative electron donors to photosystem i
Photosynthesis Research, 2003Co-Authors: Antonio Diazquintana, Manuel Hervas, Berta De La Cerda, José A. Navarro, Fernando P Molinaheredia, Miguel A. RosaAbstract:Plastocyanin and Cytochrome C6 are two soluble metalloproteins that act as alternative electron carriers between the membrane-embedded complexes Cytochromes b6f and Photosystem I. Despite plastocyanin and Cytochrome C6 differing in the nature of their redox center (one is a copper protein, the other is a heme protein) and folding pattern (one is a β-barrel, the other consists of α-helices), they are exchangeable in green algae and cyanobacteria. In fact, the two proteins share a number of structural similarities that allow them to interact with the same membrane complexes in a similar way. The kinetic and thermodynamic analysis of Photosystem I reduction by plastocyanin and Cytochrome C6 reveals that the same factors govern the reaction mechanism within the same organism, but differ from one another. In cyanobacteria, in particular, the electrostatic and hydrophobic interactions between Photosystem I and its electron donors have been analyzed using the wild-type protein species and site-directed mutants. A number of residues similarly conserved in the two proteins have been shown to be critical for the electron transfer reaction. Cytochrome C6 does contain two functional areas that are equivalent to those previously described in plastocyanin: one is a hydrophobic patch for electron transfer (site 1), and the other is an electrically charged area for complex formation (site 2). Each cyanobacterial protein contains just one arginyl residue, similarly located between sites 1 and 2, that is essential for the redox interaction with Photosystem I.
Manuel Hervas - One of the best experts on this subject based on the ideXlab platform.
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the heterologous expression of a plastocyanin in the diatom phaeodactylum tricornutum improves cell growth under iron deficient conditions
Physiologia Plantarum, 2021Co-Authors: Carmen Castell, Manuel Hervas, Jose M. Ortega, Mercedes Roncel, Pilar Bernalbayard, José A. NavarroAbstract:We have investigated if the heterologous expression of a functional green alga plastocyanin in the diatom Phaeodactylum tricornutum can improve photosynthetic activity and cell growth. Previous in vitro assays showed that a single-mutant of the plastocyanin from the green algae Chlamydomonas reinhardtii is effective in reducing P. tricornutum photosystem I. In this study, in vivo assays with P. tricornutum strains expressing this plastocyanin indicate that even the relatively low intracellular concentrations of holo-plastocyanin detected (≈4 μM) are enough to promote an increased growth (up to 60%) under iron-deficient conditions as compared with the WT strain, measured as higher cell densities, content in pigments and active photosystem I, global photosynthetic rates per cell, and even cell volume. In addition, the presence of plastocyanin as an additional photosynthetic electron carrier seems to decrease the over-reduction of the plastoquinone pool. Consequently, it promotes an improvement in the maximum quantum yield of both photosystem II and I, together with a decrease in the acceptor side photoinhibition of photosystem II-also associated to a reduced oxidative stress-a decrease in the peroxidation of membrane lipids in the choroplast, and a lower degree of limitation on the donor side of photosystem I. Thus the heterologous plastocyanin appears to act as a functional electron carrier, alternative to the native Cytochrome C6 , under iron-limiting conditions.
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iron deficiency induces a partial inhibition of the photosynthetic electron transport and a high sensitivity to light in the diatom phaeodactylum tricornutum
Frontiers in Plant Science, 2016Co-Authors: Mercedes Roncel, Manuel Hervas, José A. Navarro, Antonio A Gonzalezrodriguez, Belen Naranjo, Pilar Bernalbayard, Anna Marika Lindahl, Jose M. OrtegaAbstract:Iron limitation is the major factor controlling phytoplankton growth in vast regions of the contemporary oceans. In this study, a combination of thermoluminescence, chlorophyll fluorescence and P700 absorbance measurements have been used to elucidate the effects of iron deficiency in the photosynthetic electron transport of the marine diatom Phaeodactylum tricornutum. Thermoluminescence was used to determine the effects of iron deficiency on Photosystem II activity. Excitation of iron-replete Phaeodactylum tricornutum cells with single turn-over flashes induced the appearance of thermoluminescence glow curves with two components with different peaks of temperature and contributions to the total signal intensity: the B band (23 oC, 63%), and the AG band (40 oC, 37%). Iron limitation did not significantly alter these bands, but induced a decrease of the total thermoluminescence signal. Far red excitation did not increase the amount of the AG band in iron-limited cells, as observed for iron-replete cells. The effect of iron deficiency on the photosystem I activity was also examined by measuring the changes in P700 redox state during illumination. The electron donation to photosystem I was substantially reduced in iron-deficient cells. This could be related with the important decline on Cytochrome C6 content observed in these cells. Iron deficiency also induced a marked increase in light sensitivity in Phaeodactylum tricornutum cells. A drastic increase in the level of peroxidation of chloroplast lipids was detected in iron-deficient cells even when grown under standard conditions at low light intensity. Illumination with a light intensity of 300 E m-2 s-1 during different time periods caused a dramatic disappearance in thermoluminescence signal in cells grown under low iron concentration, this treatment not affecting to the signal in iron-replete cells. The results of this work suggest that iron deficiency induces partial blocking of the electron transfer between photosystem II and photosystem I, due to a lower concentration of the electron donor Cytochrome C6. This decreased electron transfer may induce the over-reduction of the plastoquinone pool and consequently the appearance of acceptor side photoinhibition in photosystem II even at low light intensities. The functionality of chlororespiratory electron transfer pathway under iron restricted conditions is also discussed
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redox properties of arabidopsis Cytochrome C6 are independent of the loop extension specific to higher plants
Biochimica et Biophysica Acta, 2004Co-Authors: Jurgen Wastl, Manuel Hervas, José A. Navarro, Miguel A. Rosa, Fernando P Molinaheredia, Derek S Bendall, Christopher J HoweAbstract:Cytochrome C6 (cytC6) from Arabidopsis differs from the cyanobacterial and algal homologues in several redox properties. It is possible that these differences might be due to the presence of a 12 amino acid residue loop extension common to higher plant cytC6 proteins. However, homology modelling suggests this is not the case. We report experiments to test if differences in biochemical properties could be due to this extension. Analysis of mutant forms of Arabidopsis cytC6 in which the entire extension was lacking, or a pair of cysteine residues in the extension had been exchanged for serine, revealed no significant effect of these changes on either the redox potential of the haem group or the reactivity towards Photosystem I (PSI). We conclude that the differences in properties are due to more subtle unidentified differences in structure, and that the sequence extension in the higher plant proteins has a function yet to be identified.
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the efficient functioning of photosynthesis and respiration in synechocystis sp pcc 6803 strictly requires the presence of either Cytochrome C6 or plastocyanin
Journal of Biological Chemistry, 2004Co-Authors: Raul V Duran, Manuel Hervas, Miguel A. Rosa, José A. NavarroAbstract:In cyanobacteria, Cytochrome C6 and plastocyanin are able to replace each other as redox carriers in the photosynthetic and respiratory electron transport chains with the synthesis of one or another protein being regulated by the copper concentration in the culture medium. However, the presence of a third unidentified electron carrier has been suggested. To address this point, we have constructed two deletion mutants of the cyanobacterium Synechocystis sp. PCC 6803, each variant lacking either the petE or petJ gene, which respectively codes for the copper or heme protein. The photoautotrophic and heterotrophic growth rate of the two mutants in copper-free and copper-supplemented medium as well as their photosystem I reduction kinetics in vivo were compared with those of wild-type cells. The two mutant strains grow at equivalent rates and show similar in vivo photosystem I reduction kinetics as wild-type cells when cultured in media that allow the expression of just one of the two electron donor proteins, but their ability to grow and reduce photosystem I is much lower when neither Cytochrome C6 nor plastocyanin is expressed. These findings indicate that the normal functioning of the cyanobacterial photosynthetic and respiratory chains obligatorily depends on the presence of either Cytochrome C6 or plastocyanin.
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a comparative structural and functional analysis of cyanobacterial plastocyanin and Cytochrome c 6 as alternative electron donors to photosystem i
Photosynthesis Research, 2003Co-Authors: Antonio Diazquintana, Manuel Hervas, Berta De La Cerda, José A. Navarro, Fernando P Molinaheredia, Miguel A. RosaAbstract:Plastocyanin and Cytochrome C6 are two soluble metalloproteins that act as alternative electron carriers between the membrane-embedded complexes Cytochromes b6f and Photosystem I. Despite plastocyanin and Cytochrome C6 differing in the nature of their redox center (one is a copper protein, the other is a heme protein) and folding pattern (one is a β-barrel, the other consists of α-helices), they are exchangeable in green algae and cyanobacteria. In fact, the two proteins share a number of structural similarities that allow them to interact with the same membrane complexes in a similar way. The kinetic and thermodynamic analysis of Photosystem I reduction by plastocyanin and Cytochrome C6 reveals that the same factors govern the reaction mechanism within the same organism, but differ from one another. In cyanobacteria, in particular, the electrostatic and hydrophobic interactions between Photosystem I and its electron donors have been analyzed using the wild-type protein species and site-directed mutants. A number of residues similarly conserved in the two proteins have been shown to be critical for the electron transfer reaction. Cytochrome C6 does contain two functional areas that are equivalent to those previously described in plastocyanin: one is a hydrophobic patch for electron transfer (site 1), and the other is an electrically charged area for complex formation (site 2). Each cyanobacterial protein contains just one arginyl residue, similarly located between sites 1 and 2, that is essential for the redox interaction with Photosystem I.
Miguel A. Rosa - One of the best experts on this subject based on the ideXlab platform.
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an nmr based docking model for the physiological transient complex between Cytochrome f and Cytochrome C6
FEBS Letters, 2005Co-Authors: Irene Diazmoreno, Antonio Diazquintana, Marcellus Ubbink, Miguel A. RosaAbstract:Abstract The physiological transient complex between Cytochrome f (C f ) and Cytochrome c 6 (C c 6 ) from the cyanobacterium Nostoc sp. PCC 7119 has been analysed by NMR spectroscopy. The binding constant at low ionic strength is 8 ± 2 mM −1 , and the binding site of C c 6 for C f is localized around its exposed haem edge. On the basis of the experimental data, the resulting docking simulations suggest that C c 6 binds to C f in a fashion that is analogous to that of plastocyanin but differs between prokaryotes and eukaryotes.
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NMR Analysis of the Transient Complex between Membrane Photosystem I and Soluble Cytochrome C6
'American Society for Biochemistry & Molecular Biology (ASBMB)', 2005Co-Authors: Díaz-moreno Irene, Miguel A. Rosa, Nieto P. M., Díaz-quintana Antonio, Molina-heredia, Fernando P., Hansson Örjan, Göran Karlsson B.Abstract:7 páginas, 6 figurasA structural analysis of the surface areas of Cytochrome C6, responsible for the transient interaction with photosystem I, was performed by NMR transverse relaxation-optimized spectroscopy. The hemeprotein was titrated by adding increasing amounts of the chlorophyllic photosystem, and the NMR spectra of the free and bound protein were analyzed in a comparative way. The NMR signals of Cytochrome C6 residues located at the hydrophobic and electrostatic patches, which both surround the heme cleft, were specifically modified by binding. The backbones of internal residues close to the hydrophobic patch of Cytochrome C6 were also affected, a fact that is ascribed to the conformational changes taking place inside the hemeprotein when interacting with photosystem I. To the best of our knowledge, this is the first structural analysis by NMR spectroscopy of a transient complex between soluble and membrane proteins.This work was supported by European Commission Grant HPRN-CT1999-00095, Spanish Ministry of Education, Culture and Sports Grant AP2000-2937, Spanish Ministry of Science and Technology Grant BMC2003-00458, and the Andalusian Government Grant PAI, CVI-0198.Peer reviewe
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redox properties of arabidopsis Cytochrome C6 are independent of the loop extension specific to higher plants
Biochimica et Biophysica Acta, 2004Co-Authors: Jurgen Wastl, Manuel Hervas, José A. Navarro, Miguel A. Rosa, Fernando P Molinaheredia, Derek S Bendall, Christopher J HoweAbstract:Cytochrome C6 (cytC6) from Arabidopsis differs from the cyanobacterial and algal homologues in several redox properties. It is possible that these differences might be due to the presence of a 12 amino acid residue loop extension common to higher plant cytC6 proteins. However, homology modelling suggests this is not the case. We report experiments to test if differences in biochemical properties could be due to this extension. Analysis of mutant forms of Arabidopsis cytC6 in which the entire extension was lacking, or a pair of cysteine residues in the extension had been exchanged for serine, revealed no significant effect of these changes on either the redox potential of the haem group or the reactivity towards Photosystem I (PSI). We conclude that the differences in properties are due to more subtle unidentified differences in structure, and that the sequence extension in the higher plant proteins has a function yet to be identified.
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the efficient functioning of photosynthesis and respiration in synechocystis sp pcc 6803 strictly requires the presence of either Cytochrome C6 or plastocyanin
Journal of Biological Chemistry, 2004Co-Authors: Raul V Duran, Manuel Hervas, Miguel A. Rosa, José A. NavarroAbstract:In cyanobacteria, Cytochrome C6 and plastocyanin are able to replace each other as redox carriers in the photosynthetic and respiratory electron transport chains with the synthesis of one or another protein being regulated by the copper concentration in the culture medium. However, the presence of a third unidentified electron carrier has been suggested. To address this point, we have constructed two deletion mutants of the cyanobacterium Synechocystis sp. PCC 6803, each variant lacking either the petE or petJ gene, which respectively codes for the copper or heme protein. The photoautotrophic and heterotrophic growth rate of the two mutants in copper-free and copper-supplemented medium as well as their photosystem I reduction kinetics in vivo were compared with those of wild-type cells. The two mutant strains grow at equivalent rates and show similar in vivo photosystem I reduction kinetics as wild-type cells when cultured in media that allow the expression of just one of the two electron donor proteins, but their ability to grow and reduce photosystem I is much lower when neither Cytochrome C6 nor plastocyanin is expressed. These findings indicate that the normal functioning of the cyanobacterial photosynthetic and respiratory chains obligatorily depends on the presence of either Cytochrome C6 or plastocyanin.
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a comparative structural and functional analysis of cyanobacterial plastocyanin and Cytochrome c 6 as alternative electron donors to photosystem i
Photosynthesis Research, 2003Co-Authors: Antonio Diazquintana, Manuel Hervas, Berta De La Cerda, José A. Navarro, Fernando P Molinaheredia, Miguel A. RosaAbstract:Plastocyanin and Cytochrome C6 are two soluble metalloproteins that act as alternative electron carriers between the membrane-embedded complexes Cytochromes b6f and Photosystem I. Despite plastocyanin and Cytochrome C6 differing in the nature of their redox center (one is a copper protein, the other is a heme protein) and folding pattern (one is a β-barrel, the other consists of α-helices), they are exchangeable in green algae and cyanobacteria. In fact, the two proteins share a number of structural similarities that allow them to interact with the same membrane complexes in a similar way. The kinetic and thermodynamic analysis of Photosystem I reduction by plastocyanin and Cytochrome C6 reveals that the same factors govern the reaction mechanism within the same organism, but differ from one another. In cyanobacteria, in particular, the electrostatic and hydrophobic interactions between Photosystem I and its electron donors have been analyzed using the wild-type protein species and site-directed mutants. A number of residues similarly conserved in the two proteins have been shown to be critical for the electron transfer reaction. Cytochrome C6 does contain two functional areas that are equivalent to those previously described in plastocyanin: one is a hydrophobic patch for electron transfer (site 1), and the other is an electrically charged area for complex formation (site 2). Each cyanobacterial protein contains just one arginyl residue, similarly located between sites 1 and 2, that is essential for the redox interaction with Photosystem I.
M A De La Rosa - One of the best experts on this subject based on the ideXlab platform.
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site directed mutants of Cytochrome C6 provide new insights into the interaction between psi and the hemeprotein
1998Co-Authors: B De La Cerda, Manuel Hervas, José A. Navarro, Antonio Diazquintana, Fernando P Molinaheredia, M A De La RosaAbstract:In some cyanobacteria and green algae, plastocyanin (Pc) and Cytochrome C6 (Cyt) act as alternative electron donors to PSI. The two metalloproteins are acidic in green algae, as is Pc in higher plants, but can be either basic or acidic in cyanobacteria (see ref. [1] for a recent review).
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Kinetic Mechanisms of Psi Reduction by Plastocyanin and Cytochrome C6 in the Ancient Cyanobacteria Pseudanabaena sp. Pcc 6903 and Prochlorothrix hollandica
Photosynthesis: Mechanisms and Effects, 1998Co-Authors: José A. Navarro, M. Hervá, C. R. Babu, Fernando P. Molina-heredia, George S. Bullerjahn, M A De La RosaAbstract:Cytochrome C6 (Cyt) and plastocyanin (Pc) act as mobile electron carriers between the Cytochrome b d f and PSI complexes. Whereas some cyanobacteria and alga can synthesize both electron donors and other cyanobacteria just produce Cyt, in higher plants Pc is only found. Pc and Cyt are acidic in eukaryotic organisms, but can be either acidic, basic or neutral in cyanobacteria. Both molecules are thus an excellent example of convergent evolution of proteins with different structures but playing the same function [1].
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co evolution of Cytochrome c 6 and plastocyanin mobile proteins transferring electrons from Cytochrome b 6 f to photosystem i
Journal of Biological Inorganic Chemistry, 1997Co-Authors: José A. Navarro, Manuel Hervas, M A De La RosaAbstract:Cytochrome C6 and plastocyanin are soluble metalloproteins that act as mobile carriers transferring electrons between the two membrane-embedded photosynthetic complexes Cytochrome b6 f and photosystem I (PSI). First, an account of recent data on structural and functional features of these two membrane complexes is presented. Afterwards, attention is focused on the mobile heme and copper proteins – and, in particular, on the structural factors that allow recognition and confer molecular specificity and control the rates of electron transfer from and to the membrane complexes. The interesting question of why plastocyanin has been chosen over the ancient heme protein is discussed to place emphasis on the evolutionary aspects. In fact, Cytochrome C6 and plastocyanin are presented herein as an excellent case study of biological evolution, which is not only convergent (two different structures but the same physiological function), but also parallel (two proteins adapting themselves to vary accordingly to each other within the same organism).
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co evolution of Cytochrome C6 and plastocyanin mobile proteins transferring electrons from Cytochrome b6f to photosystem i
Journal of Biological Inorganic Chemistry, 1997Co-Authors: José A. Navarro, Manuel Hervas, M A De La RosaAbstract:Cytochrome C6 and plastocyanin are soluble metalloproteins that act as mobile carriers transferring electrons between the two membrane-embedded photosynthetic complexes Cytochrome b6 f and photosystem I (PSI). First, an account of recent data on structural and functional features of these two membrane complexes is presented. Afterwards, attention is focused on the mobile heme and copper proteins – and, in particular, on the structural factors that allow recognition and confer molecular specificity and control the rates of electron transfer from and to the membrane complexes. The interesting question of why plastocyanin has been chosen over the ancient heme protein is discussed to place emphasis on the evolutionary aspects. In fact, Cytochrome C6 and plastocyanin are presented herein as an excellent case study of biological evolution, which is not only convergent (two different structures but the same physiological function), but also parallel (two proteins adapting themselves to vary accordingly to each other within the same organism).
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ab initio determination of the crystal structure of Cytochrome C6 and comparison with plastocyanin
Structure, 1995Co-Authors: Carlos Frazao, José A. Navarro, Maria Armenia Carrondo, M A De La Rosa, Claudio M Soares, Ehmke Pohl, Z Dauter, Keith S Wilson, M Herves, George M. SheldrickAbstract:Abstract Background: Electron transfer between Cytochrome f and photosystem I (PSI) can be accomplished by the heme-containing protein Cytochrome c 6 or by the copper-containing protein plastocyanin. Higher plants use plastocyanin as the only electron donor to PSI, whereas most green algae and cyanobacteria can use either, with similar kinetics, depending on the copper concentration in the culture medium. Results We report here the determination of the structure of Cytochrome c 6 from the green alga Monoraphidium braunii. Synchrotron X-ray data with an effective resolution of 1.2 a and the presence of one iron and three sulfur atoms enabled, possibly for the first time, the determination of an unknown protein structure by ab initio methods. Anisotropic refinement was accompanied by a decrease in the ‘free' R value of over 7%; the anisotropic motion is concentrated at the termini and between residues 38 and 53. The heme geometry is in very good agreement with a new set of heme distances derived from the structures of small molecules. This is probably the most precise structure of a heme protein to date. Conclusion On the basis of this Cytochrome c 6 structure, we have calculated potential electron transfer pathways and made comparisons with similar analyses for plastocyanin. Electron transfer between the copper redox center of plastocyanin to PSI and from Cytochrome f is believed to involve two sites on the protein. In contrast, Cytochrome c 6 may well use just one electron transfer site, close to the heme unit, in its corresponding reactions with the same two redox partners.
Michael Hippler - One of the best experts on this subject based on the ideXlab platform.
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residues psab asp612 and psab glu613 of photosystem i confer ph dependent binding of plastocyanin and Cytochrome c 6
Biochemistry, 2012Co-Authors: Sebastian Kuhlgert, Friedel Drepper, Frederik Sommer, Christian Fufezan, Michael HipplerAbstract:The binding and electron transfer between plastocyanin (pc) or Cytochrome C6 (cyt C6) and photosystem I (PSI) can be described by hydrophobic as well as electrostatic interactions. The two α helices, l and l′ in PsaB and PsaA, respectively, are involved in forming the hydrophobic interaction site at the oxidizing site of PSI. To obtain mechanistic insights into the function of the two negatively charged residues D612 and E613, present in α helix l of PsaB, we exchanged both residues by site-directed mutagenesis with His and transformed a PsaB deficient mutant of Chlamydomonas reinhardtii. Flash-induced absorption spectroscopy revealed that PSI harboring the changes D612H and E613H had a high affinity toward binding of the electron donors and possessed an altered pH dependence of electron transfer with pc and cyt C6. Despite optimized binding and electron transfer between the altered PSI and its electron donors, the mutant strain PsaB-D612H/E613H exhibited a strong light sensitive growth phenotype, indicat...
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the hydrophobic recognition site formed by residues psaa trp651 and psab trp627 of photosystem i in chlamydomonas reinhardtii confers distinct selectivity for binding of plastocyanin and Cytochrome C6
Journal of Biological Chemistry, 2004Co-Authors: Frederik Sommer, Wolfgang Haehnel, Friedel Drepper, Michael HipplerAbstract:Abstract On the lumenal side of photosystem I (PSI), each of the two large core subunits, PsaA and PsaB, expose a conserved tryptophan residue to the surface. PsaB-Trp627 is part of the hydrophobic recognition site that is essential for tight binding of the two electron donors plastocyanin and Cytochrome C6 to the donor side of PSI (Sommer, F., Drepper, F., and Hippler, M. (2002) J. Biol. Chem. 277, 6573–6581). To examine the function of PsaA-Trp651 in binding and electron transfer of both donors to PSI, we generated the mutants PsaA-W651F and PsaA-W651S by site-directed mutagenesis and biolistic transformation of Chlamydomonas reinhardtii. The protein-protein interaction and the electron transfer between the donors and PSI isolated from the mutants were analyzed by flash absorption spectroscopy. The mutation PsaA-W651F completely abolished the formation of a first order electron transfer complex between plastocyanin (pc) and the altered PSI and increased the dissociation constant for binding of Cytochrome (cyt) C6 by more than a factor of 10 as compared with wild type. Mutation of PsaA-Trp651 to Ser had an even larger impact on the dissociation constant. The KD value increased another 2-fold when the values obtained for the interaction and electron transfer between cyt C6 and PSI from PsaA-W651S and PsaA-W651F are compared. In contrast, binding and electron transfer of pc to PSI from PsaA-W651S improved as compared with PSI from PsaA-W651F and admitted the formation of an inter-molecular electron transfer complex, resulting in a KD value of about 554 μm that is still five times higher than observed for wild type. These results demonstrate that PsaA-Trp651 is, such as PsaB-Trp627, crucial for high affinity binding of pc and cyt C6 to PSI. Our results also indicate that the highly conserved structural recognition motif that is formed by PsaA-Trp651 and PsaB-Trp627 confers a differential selectivity in binding of both donors to PSI.
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the luminal helix l of psab is essential for recognition of plastocyanin or Cytochrome C6 and fast electron transfer to photosystem i in chlamydomonas reinhardtii
Journal of Biological Chemistry, 2002Co-Authors: Frederik Sommer, Friedel Drepper, Michael HipplerAbstract:Abstract At the lumenal side of photosystem I (PSI) in cyanobacteria, algae, and vascular plants, proper recognition and binding of the donor proteins plastocyanin (pc) and Cytochrome (cyt) c 6 are crucial to allow subsequent efficient electron transfer to the photooxidized primary donor. To characterize the surface regions of PSI needed for the correct binding of both donors, loop j of PsaB of Chlamydomonas reinhardtii was modified using site-directed mutagenesis and chloroplast transformation. Mutant strains D624K, E613K/D624K, E613K/W627F, and D624K/W627F accumulated 50% of PSI as compared with wild type. This was sufficient to isolate the altered PSI and perform a detailed analysis of the electron transfer between the modified PSI and the two algal donors using flash-induced spectroscopy. Such an analysis indicated that residue Glu613 of PsaB has two functions: (i) it is crucial for an improved unbinding of the two donors from PSI, and (ii) it orientates the positively charged N-terminal domain of PsaF in a way that allows efficient binding of pc or cyt c 6 to PSI. Mutation of Trp627 to Phe completely abolishes the formation of an intermolecular electron transfer complex between pc and PSI and also drastically diminishes the rate of electron transfer between the donor and PSI. This mutation also hinders binding and electron transfer between the altered PSI and cytc 6. It causes a 10-fold increase of the half-time of electron transfer within the intermolecular complex of cytc 6 and PSI. These data strongly suggest that Trp627 is a key residue of the recognition site formed by the core of PSI for binding and electron transfer between the two soluble electron donors and the photosystem.
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the n terminal domain of psaf precise recognition site for binding and fast electron transfer from Cytochrome C6 and plastocyanin to photosystem i of chlamydomonas reinhardtii
Proceedings of the National Academy of Sciences of the United States of America, 1998Co-Authors: Michael Hippler, Wolfgang Haehnel, Friedel Drepper, Jean-david RochaixAbstract:The PsaF-deficient mutant 3bF of Chlamydomonas reinhardtii was used to modify PsaF by nuclear transformation and site-directed mutagenesis. Four lysine residues in the N-terminal domain of PsaF, which have been postulated to form the positively charged face of a putative amphipathic α-helical structure were altered to K12P, K16Q, K23Q, and K30Q. The interactions between plastocyanin (pc) or Cytochrome C6 (cyt C6) and photosystem I (PSI) isolated from wild type and the different mutants were analyzed using crosslinking techniques and flash absorption spectroscopy. The K23Q change drastically affected crosslinking of pc to PSI and electron transfer from pc and cyt C6 to PSI. The corresponding second order rate constants for binding of pc and cyt C6 were reduced by a factor of 13 and 7, respectively. Smaller effects were observed for mutations K16Q and K30Q, whereas in K12P the binding was not changed relative to wild type. None of the mutations affected the half-life of the microsecond electron transfer performed within the intermolecular complex between the donors and PSI. The fact that these single amino acid changes within the N-terminal domain of PsaF have different effects on the electron transfer rate constants and dissociation constants for both electron donors suggests the existence of a rather precise recognition site for pc and cyt C6 that leads to the stabilization of the final electron transfer complex through electrostatic interactions.
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fast electron transfer from Cytochrome C6 and plastocyanin to photosystem i of chlamydomonas reinhardtii requires psaf
Biochemistry, 1997Co-Authors: Michael Hippler, Friedel Drepper, Joseph Farah, Jean-david RochaixAbstract:To study the function of the PsaF subunit of photosystem I (PSI), the interactions between plastocyanin or Cytochrome C6 and PSI isolated from wild-type and a PsaF-deficient mutant of Chlamydomonas...
