The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform
Gernot Renger - One of the best experts on this subject based on the ideXlab platform.
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Photosystem II: The machinery of photosynthetic water splitting
Photosynthesis Research, 2008Co-Authors: Gernot Renger, Thomas RengerAbstract:This review summarizes our current state of knowledge on the structural organization and functional pattern of photosynthetic water splitting in the multimeric Photosystem II (PS II) complex, which acts as a light-driven water: plastoquinone-oxidoreductase. The overall process comprises three types of reaction sequences: (1) photon absorption and excited singlet state trapping by charge separation leading to the ion radical pair $$ {\text{P}}680^{ + \bullet } {\text{Q}}_{\text{A}}^{ - \bullet } \left( { \overset{\wedge}{=}{\text{P}}_{\text{D1}}^{ + \bullet } {\text{Q}}_{\text{A}}^{ - \bullet } } \right) $$ formation, (2) oxidative water splitting into four protons and molecular dioxygen at the water oxidizing complex (WOC) with $$ {\text{P}}680^{ + \bullet } $$ as driving force and tyrosine Y_Z as intermediary Redox Carrier, and (3) reduction of plastoquinone to plastoquinol at the special Q_B binding site with $$ {\text{Q}}_{\text{A}}^{ - \bullet } $$ acting as reductant. Based on recent progress in structure analysis and using new theoretical approaches the mechanism of reaction sequence (1) is discussed with special emphasis on the excited energy transfer pathways and the sequence of charge transfer steps: $$ ^{1} \left( {\text{RC-PC}} \right)^{ *} {\text{Q}}_{\text{A}} \to {\text{P}}_{{{\text{D}}2}} {\text{P}}_{{{\text{D}}1}} {\text{Chl}}_{{{\text{D}}1}}^{ + \bullet } {\text{Pheo}}_{{{\text{D}}1}}^{ - \bullet } {\text{Q}}_{\text{A}} \to {\text{P}}_{{{\text{D}}2}} {\text{P}}_{{{\text{D}}1}}^{ + \bullet } {\text{Chl}}_{{{\text{D}}1}} {\text{Pheo}}_{{{\text{D}}1}}^{ - \bullet } {\text{Q}}_{\text{A}} \to {\text{P}}_{{{\text{D}}2}} {\text{P}}_{{{\text{D}}1}}^{ + \bullet } {\text{Chl}}_{\text{D1}} {\text{Pheo}}_{\text{D1}} {\text{Q}}_{\text{A}}^{ - \bullet } , $$ where ^1(RC-PC)* denotes the excited singlet state ^1P680* of the reaction centre pigment complex. The structure of the catalytic Mn_4O_ X Ca cluster of the WOC and the four step reaction sequence leading to oxidative water splitting are described and problems arising for the electronic configuration, in particular for the nature of Redox state S_3, are discussed. The unravelling of the mode of O–O bond formation is of key relevance for understanding the mechanism of the process. This problem is not yet solved. A multistate model is proposed for S_3 and the functional role of proton shifts and hydrogen bond network(s) is emphasized. Analogously, the structure of the Q_B site for PQ reduction to PQH_2 and the energetic and kinetics of the two step Redox reaction sequence are described. Furthermore, the relevance of the protein dynamics and the role of water molecules for its flexibility are briefly outlined. We end this review by presenting future perspectives on the water oxidation process.
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Chapter 17:Photosynthetic Water Splitting
Comprehensive Series in Photochemical & Photobiological Sciences, 2007Co-Authors: Johannes Messinger, Gernot RengerAbstract:This chapter reviews our current state of knowledge on the structure and functional pattern of the water oxidizing complex (WOC) in photosynthesis. The reactions leading to oxidative water splitting into molecular oxygen and four protons take place at a multimeric metal center, the Mn4OxCa cluster (x symbolizes the number of oxo-bridges). The overall process consists of a reaction sequence of four oxidation steps (Kok cycle), which is energetically driven by the strongly oxidizing cation radical P680+˙ with tyrosine YZ acting as intermediary Redox Carrier. The energetics and kinetics of these reactions are described. Based on the Kok-scheme as a fingerprint for the interpretation of spectroscopic data, information is obtained on the electronic configuration and nuclear geometry of the different Redox states Si, in particular on the valence states and the distances between the metal centers. Furthermore, the exchange kinetics of substrate water in the Si states are presented. The transitions S0 → S1 and S1 → S2 are shown to be metal-centered Redox steps, while S2 → S3 is favored to be a ligand-centered reaction. The Redox states S3 and/or S3YZOX could comprise Redox isomerism and tautomerism equilibria. Finally, we attempt to cast our current knowledge about photosynthetic water splitting into a mechanism.
Irene Díaz-moreno - One of the best experts on this subject based on the ideXlab platform.
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Cytochrome c6 of Cyanobacteria and Algae: From the Structure to the Interaction
Advances in Photosynthesis and Respiration, 2020Co-Authors: Irene Díaz-moreno, Antonio Díaz-quintana, Miguel A. De La RosaAbstract:Cytochrome c6 is a small, globular and soluble hemeprotein—found in algae and cyanobacteria, but not in higher plants—that usually serves as a Redox Carrier between the cytochrome b6f complex and photosystem I in the photosynthetic electron transport chain. In cyanobacteria, in particular, it can also donate electrons to cytochrome c oxidase and can thus serve as a switch between photosynthesis and respiration as these two processes share the same cellular location.
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Tyrosine phosphorylation turns alkaline transition into a biologically relevant process and makes human cytochrome c behave as an anti-apoptotic switch
JBIC Journal of Biological Inorganic Chemistry, 2011Co-Authors: José M. García-heredia, Antonio Díaz-quintana, Miguel A. De La Rosa, Maria Salzano, Mar Orzáez, Enrique Pérez-payá, Miguel Teixeira, Irene Díaz-morenoAbstract:Cytochrome c (C c ) is a key protein in cell life (respiration) and cell death (apoptosis). On the one hand, it serves as a mitochondrial Redox Carrier, transferring electrons between the membrane-embedded complexes III and IV. On the other hand, it acts as a cytoplasmic apoptosis-triggering agent, forming the apoptosome with apoptosis protease-activating factor-1 (Apaf-1) and activating the caspase cascade. The two functions of cytochrome c are finely tuned by the phosphorylation of tyrosines and, in particular, those located at positions 48 and 97. However, the specific cytochrome c -phosphorylating kinase is still unknown. To study the structural and functional changes induced by tyrosine phosphorylation in cytochrome c , we studied the two phosphomimetic mutants Y48E and Y97E, in which each tyrosine residue is replaced by glutamate. Such substitutions alter both the physicochemical features and the function of each mutant compared with the native protein. Y97E is significantly less stable than the WT species, whereas Y48E not only exhibits lower values for the alkaline transition p K _a and the midpoint Redox potential, but it also impairs Apaf-1-mediated caspase activation. Altogether, these findings suggest that the specific phosphorylation of Tyr48 makes cytochrome c act as an anti-apoptotic switch.
Thomas Renger - One of the best experts on this subject based on the ideXlab platform.
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Photosystem II: The machinery of photosynthetic water splitting
Photosynthesis Research, 2008Co-Authors: Gernot Renger, Thomas RengerAbstract:This review summarizes our current state of knowledge on the structural organization and functional pattern of photosynthetic water splitting in the multimeric Photosystem II (PS II) complex, which acts as a light-driven water: plastoquinone-oxidoreductase. The overall process comprises three types of reaction sequences: (1) photon absorption and excited singlet state trapping by charge separation leading to the ion radical pair $$ {\text{P}}680^{ + \bullet } {\text{Q}}_{\text{A}}^{ - \bullet } \left( { \overset{\wedge}{=}{\text{P}}_{\text{D1}}^{ + \bullet } {\text{Q}}_{\text{A}}^{ - \bullet } } \right) $$ formation, (2) oxidative water splitting into four protons and molecular dioxygen at the water oxidizing complex (WOC) with $$ {\text{P}}680^{ + \bullet } $$ as driving force and tyrosine Y_Z as intermediary Redox Carrier, and (3) reduction of plastoquinone to plastoquinol at the special Q_B binding site with $$ {\text{Q}}_{\text{A}}^{ - \bullet } $$ acting as reductant. Based on recent progress in structure analysis and using new theoretical approaches the mechanism of reaction sequence (1) is discussed with special emphasis on the excited energy transfer pathways and the sequence of charge transfer steps: $$ ^{1} \left( {\text{RC-PC}} \right)^{ *} {\text{Q}}_{\text{A}} \to {\text{P}}_{{{\text{D}}2}} {\text{P}}_{{{\text{D}}1}} {\text{Chl}}_{{{\text{D}}1}}^{ + \bullet } {\text{Pheo}}_{{{\text{D}}1}}^{ - \bullet } {\text{Q}}_{\text{A}} \to {\text{P}}_{{{\text{D}}2}} {\text{P}}_{{{\text{D}}1}}^{ + \bullet } {\text{Chl}}_{{{\text{D}}1}} {\text{Pheo}}_{{{\text{D}}1}}^{ - \bullet } {\text{Q}}_{\text{A}} \to {\text{P}}_{{{\text{D}}2}} {\text{P}}_{{{\text{D}}1}}^{ + \bullet } {\text{Chl}}_{\text{D1}} {\text{Pheo}}_{\text{D1}} {\text{Q}}_{\text{A}}^{ - \bullet } , $$ where ^1(RC-PC)* denotes the excited singlet state ^1P680* of the reaction centre pigment complex. The structure of the catalytic Mn_4O_ X Ca cluster of the WOC and the four step reaction sequence leading to oxidative water splitting are described and problems arising for the electronic configuration, in particular for the nature of Redox state S_3, are discussed. The unravelling of the mode of O–O bond formation is of key relevance for understanding the mechanism of the process. This problem is not yet solved. A multistate model is proposed for S_3 and the functional role of proton shifts and hydrogen bond network(s) is emphasized. Analogously, the structure of the Q_B site for PQ reduction to PQH_2 and the energetic and kinetics of the two step Redox reaction sequence are described. Furthermore, the relevance of the protein dynamics and the role of water molecules for its flexibility are briefly outlined. We end this review by presenting future perspectives on the water oxidation process.
Miguel A. De La Rosa - One of the best experts on this subject based on the ideXlab platform.
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Cytochrome c6 of Cyanobacteria and Algae: From the Structure to the Interaction
Advances in Photosynthesis and Respiration, 2020Co-Authors: Irene Díaz-moreno, Antonio Díaz-quintana, Miguel A. De La RosaAbstract:Cytochrome c6 is a small, globular and soluble hemeprotein—found in algae and cyanobacteria, but not in higher plants—that usually serves as a Redox Carrier between the cytochrome b6f complex and photosystem I in the photosynthetic electron transport chain. In cyanobacteria, in particular, it can also donate electrons to cytochrome c oxidase and can thus serve as a switch between photosynthesis and respiration as these two processes share the same cellular location.
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Tyrosine phosphorylation turns alkaline transition into a biologically relevant process and makes human cytochrome c behave as an anti-apoptotic switch
JBIC Journal of Biological Inorganic Chemistry, 2011Co-Authors: José M. García-heredia, Antonio Díaz-quintana, Miguel A. De La Rosa, Maria Salzano, Mar Orzáez, Enrique Pérez-payá, Miguel Teixeira, Irene Díaz-morenoAbstract:Cytochrome c (C c ) is a key protein in cell life (respiration) and cell death (apoptosis). On the one hand, it serves as a mitochondrial Redox Carrier, transferring electrons between the membrane-embedded complexes III and IV. On the other hand, it acts as a cytoplasmic apoptosis-triggering agent, forming the apoptosome with apoptosis protease-activating factor-1 (Apaf-1) and activating the caspase cascade. The two functions of cytochrome c are finely tuned by the phosphorylation of tyrosines and, in particular, those located at positions 48 and 97. However, the specific cytochrome c -phosphorylating kinase is still unknown. To study the structural and functional changes induced by tyrosine phosphorylation in cytochrome c , we studied the two phosphomimetic mutants Y48E and Y97E, in which each tyrosine residue is replaced by glutamate. Such substitutions alter both the physicochemical features and the function of each mutant compared with the native protein. Y97E is significantly less stable than the WT species, whereas Y48E not only exhibits lower values for the alkaline transition p K _a and the midpoint Redox potential, but it also impairs Apaf-1-mediated caspase activation. Altogether, these findings suggest that the specific phosphorylation of Tyr48 makes cytochrome c act as an anti-apoptotic switch.
DS Bendall - One of the best experts on this subject based on the ideXlab platform.
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The novel cytochrome c(6) of chloroplasts: a case of evolutionary bricolage?
J EXP BOT, 2006Co-Authors: DS BendallAbstract:Cytochrome c(6) has long been known as a Redox Carrier of the thylakoid lumen of cyanobacteria and some eukaryotic algae that can substitute for plastocyanin in electron transfer. Until recently, it was widely accepted that land plants lack a cytochrome c(6). However, a homologue of the protein has now been identified in several plant species together with an additional isoform in the green alga Chlamydomonas reinhardtii. This form of the protein, designated cytochrome c(6A), differs from the 'conventional' cytochrome c(6) in possessing a conserved insertion of 12 amino acids that includes two absolutely conserved cysteine residues. There are conflicting reports of whether cytochrome c(6A) can substitute for plastocyanin in photosynthetic electron transfer. The evidence for and against this is reviewed and the likely evolutionary history of cytochrome c(6A) is discussed. It is suggested that it has been converted from a primary role in electron transfer to one in regulation within the chloroplast, and is an example of evolutionary 'bricolage'.
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The novel cytochrome c6 of chloroplasts: a case of evolutionary bricolage?
Journal of Experimental Botany, 2005Co-Authors: Christopher J. Howe, Beatrix G. Schlarb-ridley, Juergen Wastl, Saul Purton, DS BendallAbstract:Cytochrome c 6 has long been known as a Redox Carrier of the thylakoid lumen of cyanobacteria and some eukaryotic algae that can substitute for plastocyanin in electron transfer. Until recently, it was widely accepted that land plants lack a cytochrome c 6 . However, a homologue of the protein has now been identified in several plant species together with an additional isoform in the green alga Chlamydomonas reinhardtii. This form of the protein, designated cytochrome c 6A , differs from the 'conventional' cytochrome c 6 in possessing a conserved insertion of 12 amino acids that includes two absolutely conserved cysteine residues. There are conflicting reports of whether cytochrome c 6A can substitute for plastocyanin in photosynthetic electron transfer. The evidence for and against this is reviewed and the likely evolutionary history of cytochrome c 6A is discussed. It is suggested that it has been converted from a primary role in electron transfer to one in regulation within the chloroplast, and is an example of evolutionary 'bricolage'.