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1.
Physiol Plant ; 166(1): 320-335, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30740703

RESUMO

Mechanisms of the complex formation between plastocyanin and cytochrome f in higher plants (Spinacia oleracea and Brassica rapa), green microalgae Chlamydomonas reinhardtii and two species of cyanobacteria (Phormidium laminosum and Nostoc sp.) were investigated using combined Brownian and molecular dynamics simulations and hierarchical cluster analysis. In higher plants and green algae, electrostatic interactions force plastocyanin molecule close to the heme of cytochrome f. In the subsequent rotation of plastocyanin molecule around the point of electrostatic contact in the vicinity of cytochrome f, copper (Cu) atom approaches cytochrome heme forming a stable configuration where cytochrome f molecule behaves as a rather rigid body without conformational changes. In Nostoc plastocyanin molecule approaches cytochrome f in a different orientation (head-on) where the stabilization of the plastocyanin-cytochrome f complex is accompanied by the conformational changes of the G188E189D190 loop that stabilizes the whole complex. In cyanobacterium P. laminosum, electrostatic preorientation of the approaching molecules was not detected, thus indicating that random motions rather than long-range electrostatic interactions are responsible for the proper mutual orientation. We demonstrated that despite the structural similarity of the investigated electron transport proteins in different photosynthetic organisms, the complexity of molecular mechanisms of the complex formation increases in the following sequence: non-heterocystous cyanobacteria - heterocystous cyanobacteria - green algae - flowering plants.


Assuntos
Clorófitas/metabolismo , Cianobactérias/metabolismo , Citocromos f/metabolismo , Plastocianina/metabolismo , Transporte de Elétrons , Oxirredução , Complexo de Proteína do Fotossistema I/metabolismo , Espectrometria de Fluorescência
2.
Dokl Biochem Biophys ; 468(1): 183-6, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-27417715

RESUMO

Electrostatic interaction of plastocyanin and cytochrome f in the process of protein-protein complex formation was investigated by computer simulation methods. It was shown that long-range electrostatic interaction promotes energetically favorable mutual orientation of protein molecules at distances between their cofactors shorter than 5 nm. At distances shorter than 3 nm, these electrostatic interactions lead to a significantly detectable increase in the rate of convergence of the cofactors.


Assuntos
Citocromos f/química , Difusão , Proteínas de Plantas/química , Plastocianina/química , Eletricidade Estática , Brassica napus , Simulação por Computador , Cobre/química , Modelos Químicos , Oxirredução , Software , Soluções , Solventes/química , Spinacia oleracea
3.
Biochim Biophys Acta ; 1857(6): 819-30, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27056771

RESUMO

Electrochromic shift measurements confirmed that the Q-cycle operated in sunflower leaves. The slow temporarily increasing post-pulse phase was recorded, when ATP synthase was inactivated in the dark and plastoquinol (PQH(2)) oxidation was initiated by a short pulse of far-red light (FRL). During illumination by red light, the Q-cycle-supported proton arrival at the lumen and departure via ATP synthase were simultaneous, precluding extreme build-up of the membrane potential. To investigate the kinetics of the Q-cycle, less than one PQH(2) per cytochrome b(6)f (Cyt b(6)f) were reduced by illuminating the leaf with strong light pulses or single-turnover Xe flashes. The post-pulse rate of oxidation of these PQH2 molecules was recorded via the rate of reduction of plastocyanin (PC(+)) and P700(+), monitored at 810 and 950 nm. The PSII-reduced PQH(2) molecules were oxidized with multi-phase overall kinetics, τ(d)=1, τ(p)=5.6 and τ(s)=16 ms (22 °C). We conclude that τ(d) characterizes PSII processes and diffusion, τ(p) is the bifurcated oxidation of the primary quinol and τ(s) is the Q-cycle-involving reduction of the secondary quinol at the n-site, its transport to the p-site, and bifurcated oxidation there. The extraordinary slow kinetics of the Q-cycle may be related to the still unsolved mechanism of the "photosynthetic control."


Assuntos
Complexo Citocromos b6f/metabolismo , Folhas de Planta/metabolismo , Proteínas de Plantas/metabolismo , Plastocianina/metabolismo , Plastoquinona/análogos & derivados , Algoritmos , Clorofila/metabolismo , Citocromos f/metabolismo , Transporte de Elétrons , Helianthus/metabolismo , Helianthus/efeitos da radiação , Cinética , Luz , Complexos de Proteínas Captadores de Luz/metabolismo , Modelos Biológicos , Oxirredução , Fotossíntese/efeitos da radiação , Complexo de Proteína do Fotossistema I/metabolismo , Folhas de Planta/efeitos da radiação , Plastoquinona/metabolismo
4.
Biofizika ; 60(4): 629-38, 2015.
Artigo em Russo | MEDLINE | ID: mdl-26394461

RESUMO

The Brownian dynamics method is used for qualitative analysis of events leading to formation of a functionally active plastocyanin-cytochrome f complex. Intermediate states of this process are identified by density-based hierarchical clustering. Diffusive entrapment of plastocyanin by cytochrome f is a key point of the suggested putative scenario of protein-protein approaching. Mobility of plastocyanin is characterized for different values of protein-protein electrostatic interaction energy.


Assuntos
Citocromos f/química , Elétrons , Simulação de Dinâmica Molecular , Plastocianina/química , Sítios de Ligação , Brassica rapa/química , Análise por Conglomerados , Difusão , Transporte de Elétrons , Oxirredução , Ligação Proteica , Estrutura Secundária de Proteína , Estrutura Terciária de Proteína , Spinacia oleracea/química , Eletricidade Estática , Termodinâmica
5.
Biofizika ; 60(2): 270-92, 2015.
Artigo em Russo | MEDLINE | ID: mdl-26016024

RESUMO

The application of Brownian dynamics for simulation of transient protein-protein interactions is reviewed. The review focuses on theoretical basics of Brownian dynamics method, its particular implementations, advantages and drawbacks of the method. The outlook for future development of Brownian dynamics-based simulation techniques is discussed. Special attention is given to analysis of Brownian dynamics trajectories. The second part of the review is dedicated to the role of Brownian dynamics simulations in studying photosynthetic electron transport. Interactions of mobile electron carriers (plastocyanin, cytochrome c6, and ferredoxin) with their reaction partners (cytochrome b6f complex, photosystem I, ferredoxin:NADP-reductase, and hydrogenase) are considered.


Assuntos
Fenômenos Biofísicos , Citocromos c6/química , Fotossíntese , Plastocianina/química , Citocromos f , Transporte de Elétrons , Ferredoxinas/química , Cinética , Modelos Moleculares , Simulação de Dinâmica Molecular , Complexo de Proteína do Fotossistema I , Conformação Proteica
6.
Proc Natl Acad Sci U S A ; 112(13): E1678-87, 2015 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-25775549

RESUMO

Chloroplast genomes encode ∼ 37 proteins that integrate into the thylakoid membrane. The mechanisms that target these proteins to the membrane are largely unexplored. We used ribosome profiling to provide a comprehensive, high-resolution map of ribosome positions on chloroplast mRNAs in separated membrane and soluble fractions in maize seedlings. The results show that translation invariably initiates off the thylakoid membrane and that ribosomes synthesizing a subset of membrane proteins subsequently become attached to the membrane in a nuclease-resistant fashion. The transition from soluble to membrane-attached ribosomes occurs shortly after the first transmembrane segment in the nascent peptide has emerged from the ribosome. Membrane proteins whose translation terminates before emergence of a transmembrane segment are translated in the stroma and targeted to the membrane posttranslationally. These results indicate that the first transmembrane segment generally comprises the signal that links ribosomes to thylakoid membranes for cotranslational integration. The sole exception is cytochrome f, whose cleavable N-terminal cpSecA-dependent signal sequence engages the thylakoid membrane cotranslationally. The distinct behavior of ribosomes synthesizing the inner envelope protein CemA indicates that sorting signals for the thylakoid and envelope membranes are distinguished cotranslationally. In addition, the fractionation behavior of ribosomes in polycistronic transcription units encoding both membrane and soluble proteins adds to the evidence that the removal of upstream ORFs by RNA processing is not typically required for the translation of internal genes in polycistronic chloroplast mRNAs.


Assuntos
Cloroplastos/metabolismo , Ribossomos/metabolismo , Tilacoides/metabolismo , Zea mays/genética , Núcleo Celular/metabolismo , Citocromos f/metabolismo , Genoma de Cloroplastos , Proteínas de Membrana/metabolismo , Hibridização de Ácido Nucleico , Análise de Sequência com Séries de Oligonucleotídeos , Fases de Leitura Aberta , Proteínas de Plantas/genética , Plastídeos/metabolismo , Biossíntese de Proteínas , Processamento de Proteína Pós-Traducional , Transporte Proteico , RNA Mensageiro/metabolismo , Solubilidade , Zea mays/metabolismo
7.
Sci Rep ; 4: 5989, 2014 Aug 08.
Artigo em Inglês | MEDLINE | ID: mdl-25103621

RESUMO

It has been known that the process of leaf senescence is accompanied by programmed cell death (PCD), and the previous study indicated that dark-induced senescence in detached leaves from rice led to the release of cytochrome f (Cyt f) from chloroplast into the cytoplasm. In this study, the effects of Cyt f on PCD were studied both in vitro and in vivo. In a cell-free system, purified Cyt f activated caspase-3-like protease and endonuclease OsNuc37, and induced DNA fragmentation. Furthermore, Cyt f-induced caspase-3-like activity could be inhibited by MG132, which suggests that the activity was attributed to the 26S proteasome. Conditional expression of Cyt f in the cytoplasm could also activate caspase-3-like activity and DNA fragmentation. Fluorescein diacetate staining and annexin V-FITC/PI double staining demonstrated that Cyt f expression in cytoplasm significantly increased the percentage of PCD protoplasts. Yeast two-hybrid screening showed that Cyt f might interact with E3-ubiquitin ligase and RPN9b, the subunits of the ubiquitin proteasome system (UPS), and other PCD-related proteins. Taken together, these results suggest that the released Cyt f from the chloroplast into the cytoplasm might activate or rescue caspase-3-like activity by interacting with the UPS, ultimately leading to the induction of PCD.


Assuntos
Caspase 3/metabolismo , Citocromos f/metabolismo , Oryza/metabolismo , Proteínas de Plantas/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Apoptose/efeitos dos fármacos , Caspase 3/química , Sistema Livre de Células , Cloroplastos/metabolismo , Citoplasma/metabolismo , Fragmentação do DNA/efeitos dos fármacos , Desoxirribonuclease I/metabolismo , Leupeptinas/farmacologia , Células Vegetais/metabolismo , Proteínas de Plantas/antagonistas & inibidores , Hipoclorito de Sódio/toxicidade
8.
Biochim Biophys Acta ; 1837(8): 1305-15, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24685428

RESUMO

The rapid transfer of electrons in the photosynthetic redox chain is achieved by the formation of short-lived complexes of cytochrome b6f with the electron transfer proteins plastocyanin and cytochrome c6. A balance must exist between fast intermolecular electron transfer and rapid dissociation, which requires the formation of a complex that has limited specificity. The interaction of the soluble fragment of cytochrome f and cytochrome c6 from the cyanobacterium Nostoc sp. PCC 7119 was studied using NMR spectroscopy and X-ray diffraction. The crystal structures of wild type, M58H and M58C cytochrome c6 were determined. The M58C variant is an excellent low potential mimic of the wild type protein and was used in chemical shift perturbation and paramagnetic relaxation NMR experiments to characterize the complex with cytochrome f. The interaction is highly dynamic and can be described as a pure encounter complex, with no dominant stereospecific complex. Ensemble docking calculations and Monte-Carlo simulations suggest a model in which charge-charge interactions pre-orient cytochrome c6 with its haem edge toward cytochrome f to form an ensemble of orientations with extensive contacts between the hydrophobic patches on both cytochromes, bringing the two haem groups sufficiently close to allow for rapid electron transfer. This model of complex formation allows for a gradual increase and decrease of the hydrophobic interactions during association and dissociation, thus avoiding a high transition state barrier that would slow down the dissociation process.


Assuntos
Citocromos c6/química , Citocromos f/química , Complexos Multiproteicos/química , Fotossíntese , Cianobactérias/química , Cianobactérias/metabolismo , Citocromos c6/metabolismo , Citocromos f/metabolismo , Transporte de Elétrons , Interações Hidrofóbicas e Hidrofílicas , Espectroscopia de Ressonância Magnética , Método de Monte Carlo , Complexos Multiproteicos/metabolismo , Plastocianina/química , Plastocianina/metabolismo , Ligação Proteica , Conformação Proteica , Mapas de Interação de Proteínas , Difração de Raios X
9.
Biochemistry ; 52(38): 6615-26, 2013 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-23984801

RESUMO

Recent studies on the electron transfer complex formed by cytochrome f and plastocyanin from Nostoc revealed that both hydrophobic and electrostatic interactions play a role in the process of complex formation. To study the balance between these two types of interactions in the encounter and the final state, the complex between plastocyanin from Phormidium laminosum and cytochrome f from Nostoc sp. PCC 7119 was investigated using NMR spectroscopy and Monte Carlo docking. Cytochrome f has a highly negative charge. Phormidium plastocyanin is similar to that from Nostoc, but the net charge of the protein is negative rather than positive. NMR titrations of Zn-substituted Phormidium plastocyanin and Nostoc cytochrome f indicated that a complex with an affinity intermediate between those of the Nostoc and Phormidium complexes is formed. Plastocyanin was found in a head-on orientation, as determined using pseudocontact shifts, similar to that in the Phormidium complex, in which the hydrophobic patch represents the main site of interaction on plastocyanin. However, the interaction in the cross-complex is dependent on electrostatics, similar to that in the Nostoc complex. The negative charge of plastocyanin decreases, but not abolishes, the attraction to cytochrome f, resulting in the formation of a more diffuse encounter complex than in the Nostoc case, as could be determined using paramagnetic relaxation spectroscopy. This work illustrates the subtle interplay of electrostatic and hydrophobic interactions in the formation of transient protein complexes. The results are discussed in the context of a model for association on the basis of hydrophobic contacts in the encounter state.


Assuntos
Citocromos f/química , Plastocianina/química , Interações Hidrofóbicas e Hidrofílicas , Simulação de Acoplamento Molecular , Método de Monte Carlo , Nostoc/química , Ressonância Magnética Nuclear Biomolecular , Eletricidade Estática
10.
J Am Chem Soc ; 135(20): 7681-92, 2013 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-23627316

RESUMO

Protein complex formation is thought to be at least a two-step process, in which the active complex is preceded by the formation of an encounter complex. The interactions in the encounter complex are usually dominated by electrostatic forces, whereas the active complex is also stabilized by noncovalent short-range forces. Here, the complex of cytochrome f and plastocyanin, electron-transfer proteins involved in photosynthesis, was studied using paramagnetic relaxation NMR spectroscopy. Spin labels were attached to cytochrome f, and the relaxation enhancements of plastocyanin nuclei were measured, demonstrating that a large part of the cytochrome f surface area is sampled by plastocyanin. In contrast, plastocyanin is always oriented with its hydrophobic patch toward cytochrome f. The complex was visualized using ensemble docking, showing that the encounter complex is stabilized by hydrophobic as well as electrostatic interactions. The results suggest a model of electrostatic preorientation before the proteins make contact, followed by the formation of an encounter complex that rapidly leads to electron-transfer active conformations by gradual increase of the overlap of nonpolar surface areas on cytochrome f and plastocyanin. In this model the distinction between the encounter and active complexes vanishes, at least in the case of electron-transfer complexes, which do not require a high degree of specificity.


Assuntos
Citocromos f/química , Ressonância Magnética Nuclear Biomolecular , Plastocianina/química , Citocromos f/isolamento & purificação , Citocromos f/metabolismo , Interações Hidrofóbicas e Hidrofílicas , Modelos Moleculares , Método de Monte Carlo , Plastocianina/metabolismo
11.
J Biol Chem ; 288(10): 7024-36, 2013 Mar 08.
Artigo em Inglês | MEDLINE | ID: mdl-23303190

RESUMO

Based on previous comparative genomic analyses, a set of nearly 600 polypeptides was identified that is present in green algae and flowering and nonflowering plants but is not present (or is highly diverged) in nonphotosynthetic organisms. The gene encoding one of these "GreenCut" proteins, CPLD38, is in the same operon as ndhL in most cyanobacteria; the NdhL protein is part of a complex essential for cyanobacterial respiration. A cpld38 mutant of Chlamydomonas reinhardtii does not grow on minimal medium, is high light-sensitive under photoheterotrophic conditions, has lower accumulation of photosynthetic complexes, reduced photosynthetic electron flow to P700(+), and reduced photochemical efficiency of photosystem II (ΦPSII); these phenotypes are rescued by a wild-type copy of CPLD38. Single turnover flash experiments and biochemical analyses demonstrated that cytochrome b6f function was severely compromised, and the levels of transcripts and polypeptide subunits of the cytochrome b6f complex were also significantly lower in the cpld38 mutant. Furthermore, subunits of the cytochrome b6f complex in mutant cells turned over much more rapidly than in wild-type cells. Interestingly, PTOX2 and NDA2, two major proteins involved in chlororespiration, were more than 5-fold higher in mutants relative to wild-type cells, suggesting a shift in the cpld38 mutant from photosynthesis toward chlororespiratory metabolism, which is supported by experiments that quantify the reduction state of the plastoquinone pool. Together, these findings support the hypothesis that CPLD38 impacts the stability of the cytochrome b6f complex and possibly plays a role in balancing redox inputs to the quinone pool from photosynthesis and chlororespiration.


Assuntos
Chlamydomonas reinhardtii/metabolismo , Complexo Citocromos b6f/metabolismo , Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Proteínas das Membranas dos Tilacoides/metabolismo , Chlamydomonas reinhardtii/genética , Clorofila/metabolismo , ATPases de Cloroplastos Translocadoras de Prótons/genética , ATPases de Cloroplastos Translocadoras de Prótons/metabolismo , Complexo Citocromos b6f/genética , Citocromos b6/genética , Citocromos b6/metabolismo , Citocromos f/genética , Citocromos f/metabolismo , Transporte de Elétrons , Expressão Gênica , Immunoblotting , Luz , Mutação , Oxirredução , Fotossíntese/genética , Fotossíntese/efeitos da radiação , Complexo de Proteínas do Centro de Reação Fotossintética/genética , Complexo de Proteína do Fotossistema I/genética , Complexo de Proteína do Fotossistema I/metabolismo , Complexo de Proteína do Fotossistema II/genética , Complexo de Proteína do Fotossistema II/metabolismo , Plastoquinona/metabolismo , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Proteínas das Membranas dos Tilacoides/genética , Tilacoides/metabolismo
12.
J Inorg Biochem ; 115: 174-81, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22883960

RESUMO

Plastocyanin (PC) from poplar leaves is present in two isoforms, PCa and PCb, which differ in sequence by amino acid replacements at locations remote from the copper center and simultaneously act in the photosynthetic electron-transport chain. We describe ultra-high resolution structures of PCa and high-resolution structures of PCb, both under oxidizing and reducing conditions at pH 4, 6 and 8. The docking on cytochrome f and photosystem I, respectively, has been modeled for both isoforms. PCa and PCb exhibit closely similar overall and active-site structures, except for a difference in the relative orientation of the acidic patches. The isoforms exhibit substantial differences in the dependence of the reduced (Cu(I)) geometry on pH. In PCa, the decrease in pH causes a gradual dissociation of His87 from Cu(I) at low pH, probably adopting a neutral tautomeric state. In PCb, the histidine remains covalently bound to Cu(I) and may adopt a doubly protonated state at low pH. The fact that both isoforms have similar although not identical functions in photosynthetic electron flows suggests that the His87 imidazole does not play a crucial role for the pathway of electron transport from cytochrome f to oxidized PC.


Assuntos
Cobre , Fotossíntese/fisiologia , Plastocianina , Populus , Cobre/química , Cobre/metabolismo , Citocromos f/química , Citocromos f/metabolismo , Concentração de Íons de Hidrogênio , Oxirredução , Complexo de Proteína do Fotossistema I/química , Complexo de Proteína do Fotossistema I/metabolismo , Plastocianina/química , Plastocianina/metabolismo , Populus/química , Populus/metabolismo , Isoformas de Proteínas/química , Isoformas de Proteínas/metabolismo
13.
Plant Cell ; 24(6): 2649-65, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22685165

RESUMO

Fe deficiency is one of several abiotic stresses that impacts plant metabolism because of the loss of function of Fe-containing enzymes in chloroplasts and mitochondria, including cytochromes, FeS proteins, and Fe superoxide dismutase (FeSOD). Two pathways increase the capacity of the Chlamydomonas reinhardtii chloroplast to detoxify superoxide during Fe limitation stress. In one pathway, MSD3 is upregulated at the transcriptional level up to 10(3)-fold in response to Fe limitation, leading to synthesis of a previously undiscovered plastid-specific MnSOD whose identity we validated immunochemically. In a second pathway, the plastid FeSOD is preferentially retained over other abundant Fe proteins, heme-containing cytochrome f, diiron magnesium protoporphyrin monomethyl ester cyclase, and Fe2S2-containing ferredoxin, demonstrating prioritized allocation of Fe within the chloroplast. Maintenance of FeSOD occurs, after an initial phase of degradation, by de novo resynthesis in the absence of extracellular Fe, suggesting the operation of salvage mechanisms for intracellular recycling and reallocation.


Assuntos
Chlamydomonas reinhardtii/genética , Chlamydomonas reinhardtii/metabolismo , Ferro/metabolismo , Superóxido Dismutase/metabolismo , Sequência de Aminoácidos , Chlamydomonas reinhardtii/efeitos dos fármacos , Proteínas de Cloroplastos/metabolismo , Cloroplastos/metabolismo , Citocromos f/metabolismo , Ferredoxinas/metabolismo , Regulação da Expressão Gênica de Plantas , Genes de Plantas , Peróxido de Hidrogênio/metabolismo , Peróxido de Hidrogênio/farmacologia , Dados de Sequência Molecular , Estresse Fisiológico , Superóxido Dismutase/genética
14.
J Eukaryot Microbiol ; 59(6): 651-3, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22726219

RESUMO

Euglena gracilis is a fresh-water flagellate possessing secondary chloroplasts of green algal origin. In contrast with organisms possessing primary plastids, mRNA levels of nucleus-encoded genes for chloroplast proteins in E. gracilis depend on neither light nor plastid function. However, it remains unknown, if all these mRNAs are trans-spliced and possess spliced leader sequence at the 5'-end and if trans-splicing depends on light or functional plastids. This study revealed that polyadenylated mRNAs encoding the chloroplast proteins glyceraldehyde-3-phosphate dehydrogenase (GapA), cytochrome f (PetA), and subunit O of photosystem II (PsbO) are trans-spliced irrespective of light or plastid function.


Assuntos
Proteínas de Cloroplastos/genética , Euglena gracilis/genética , Regulação da Expressão Gênica , Processamento de RNA , RNA Mensageiro/metabolismo , Citocromos f/genética , Euglena gracilis/metabolismo , Euglena gracilis/efeitos da radiação , Gliceraldeído-3-Fosfato Desidrogenase (Fosforiladora)/genética , Luz , Complexo de Proteína do Fotossistema II/genética , Plastídeos/metabolismo , Plastídeos/efeitos da radiação
15.
Chembiochem ; 13(9): 1312-8, 2012 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-22619165

RESUMO

Cytochrome f (Cyt f) and plastocyanin (Pc) form a highly transient complex as part of the photosynthetic redox chain. The complex from Nostoc sp. PCC 7119 was studied by NMR relaxation spectroscopy with the aim of determining the orientation of Pc relative to Cyt f. Chemical-shift-perturbation analysis showed that the presence of spin labels on the surface of Cyt f does not significantly affect the binding of Pc. The paramagnetic relaxation enhancement results are not consistent with a single orientation of Pc, thus indicating that multiple orientations must occur and suggesting that an encounter state represents a large fraction of the complex.


Assuntos
Citocromos f/metabolismo , Nostoc , Plastocianina/metabolismo , Citocromos f/química , Mesilatos/metabolismo , Modelos Moleculares , Ressonância Magnética Nuclear Biomolecular , Plastocianina/química , Ligação Proteica , Conformação Proteica
16.
Physiol Plant ; 145(3): 395-405, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22268610

RESUMO

In this study, we tested for the temporal occurrence of photosynthetic acclimation to elevated [CO2] in the flag leaf of two important cereal crops, rice and wheat. In order to characterize the temporal onset of acclimation and the basis for any observed decline in photosynthetic rate, we characterized net photosynthesis, g(s) , g(m) , C(i) /C(a) , C(i) /C(c) , V(cmax) , J(max) , cell wall thickness, content of Rubisco, cytochrome (Cyt) f, N, chlorophyll and carbohydrate, mRNA expression for rbcL and petA, activity for Rubisco, sucrose phosphate synthase (SPS) and sucrose synthase (SS) at full flag expansion, mid-anthesis and the late grain-filling stage. No acclimation was observed for either crop at full flag leaf expansion. However, at the mid-anthesis stage, photosynthetic acclimation in rice was associated with RuBP carboxylation and regeneration limitations, while wheat only had the carboxylation limitation. By grain maturation, the decline of Rubisco content and activity had contributed to RuBP carboxylation limitation of photosynthesis in both crops at elevated [CO2]; however, the sharp decrease of Rubisco enzyme activity played a more important role in wheat. Although an increase in non-structural carbohydrates did occur during these later stages, it was not consistently associated with changes in SPS and SS or photosynthetic acclimation. Rather, over time elevated [CO2] appeared to enhance the rate of N degradation and senescence so that by late-grain fill, photosynthetic acclimation to elevated [CO2] in the flag leaf of either species was complete. These data suggest that the basis for photosynthetic acclimation with elevated [CO2] may be more closely associated with enhanced rates of senescence, and, as a consequence, may be temporally dynamic, with significant species variation.


Assuntos
Aclimatação , Dióxido de Carbono/metabolismo , Oryza/fisiologia , Fotossíntese , Folhas de Planta/fisiologia , Triticum/fisiologia , Parede Celular/metabolismo , Parede Celular/fisiologia , Cloroplastos/genética , Cloroplastos/metabolismo , Citocromos f/genética , Citocromos f/metabolismo , Ativação Enzimática , Genes de Plantas , Glucosiltransferases/metabolismo , Nitrogênio/metabolismo , Oryza/enzimologia , Oryza/genética , Folhas de Planta/enzimologia , Folhas de Planta/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Ribulose-Bifosfato Carboxilase/genética , Ribulose-Bifosfato Carboxilase/metabolismo , Ribulosefosfatos/metabolismo , Sementes/genética , Sementes/metabolismo , Sementes/fisiologia , Especificidade da Espécie , Triticum/enzimologia , Triticum/genética
17.
J Inorg Biochem ; 106(1): 143-50, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22119806

RESUMO

Cytochromes c(6) and f react by three et mechanisms under similar conditions. We report temperature and viscosity effects on the protein docking and kinetics of (3)Zncyt c(6)+cyt f(III)→Zncyt c(6)(+)+cyt f(II). At 0.5-40.0°C, this reaction occurs within the persistent (associated) diprotein complex with the rate constant k(pr) and within the transient (collision) complex with the rate constant k(tr). The viscosity independence of k(pr), the donor-acceptor coupling H(ab)=(0.5±0.1)cm(-1), and reorganizational energy λ=(2.14±0.02) eV indicate true et within the persistent complex. The viscosity dependence of k(tr) and a break at 30°C in the Eyring plot for k(tr) reveal mechanisms within the transient complex that are reversibly switched by temperature change. Kramers protein friction parameters differ much for the reactions below (σ=0.3±0.1, δ=0.85±0.07) and above (σ=4.0±0.9, δ=0.40±0.06) 30°C. The transient complex(es) undergo(es) coupled et below ca. 30°C and gated et above ca. 30°C. Brownian dynamics simulations reveal two broad, dynamic ensembles of configurations "bridged" by few intermediate configurations through which the interconversion presumably occurs.


Assuntos
Citocromos c/química , Citocromos f/química , Termodinâmica , Zinco/química , Algoritmos , Chlamydomonas reinhardtii/metabolismo , Citocromos c/metabolismo , Citocromos f/metabolismo , Transporte de Elétrons , Cinética , Modelos Químicos , Modelos Moleculares , Complexos Multiproteicos/química , Complexos Multiproteicos/metabolismo , Ligação Proteica , Conformação Proteica , Temperatura , Viscosidade , Zinco/metabolismo
18.
FEBS Lett ; 586(5): 646-52, 2012 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-21889503

RESUMO

Transient complexes, with a lifetime ranging between microseconds and seconds, are essential for biochemical reactions requiring a fast turnover. That is the case of the interactions between proteins engaged in electron transfer reactions, which are involved in relevant physiological processes such as respiration and photosynthesis. In the latter, the copper protein plastocyanin acts as a soluble carrier transferring electrons between the two membrane-embedded complexes cytochrome b(6)f and photosystem I. Here we review the combination of experimental efforts in the literature to unveil the functional and structural features of the complex between cytochrome f and plastocyanin, which have widely been used as a suitable model for analyzing transient redox interactions.


Assuntos
Proteínas de Bactérias/química , Citocromos f/química , Transporte de Elétrons , Plastocianina/química , Proteínas de Bactérias/metabolismo , Citocromos f/metabolismo , Cinética , Modelos Moleculares , Complexos Multiproteicos/química , Complexos Multiproteicos/metabolismo , Plastocianina/metabolismo , Ligação Proteica , Conformação Proteica , Estrutura Terciária de Proteína
19.
Proc Natl Acad Sci U S A ; 108(50): 20248-53, 2011 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-22128333

RESUMO

The machinery that conducts the light-driven reactions of oxygenic photosynthesis is hosted within specialized paired membranes called thylakoids. In higher plants, the thylakoids are segregated into two morphological and functional domains called grana and stroma lamellae. A large fraction of the luminal volume of the granal thylakoids is occupied by the oxygen-evolving complex of photosystem II. Electron microscopy data we obtained on dark- and light-adapted Arabidopsis thylakoids indicate that the granal thylakoid lumen significantly expands in the light. Models generated for the organization of the oxygen-evolving complex within the granal lumen predict that the light-induced expansion greatly alleviates restrictions imposed on protein diffusion in this compartment in the dark. Experiments monitoring the redox kinetics of the luminal electron carrier plastocyanin support this prediction. The impact of the increase in protein mobility within the granal luminal compartment in the light on photosynthetic electron transport rates and processes associated with the repair of photodamaged photosystem II complexes is discussed.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Proteínas de Cloroplastos/metabolismo , Tilacoides/metabolismo , Arabidopsis/ultraestrutura , Citocromos f/metabolismo , Escuridão , Difusão , Cinética , Modelos Biológicos , Oxirredução , Tilacoides/ultraestrutura
20.
Biofizika ; 56(5): 775-86, 2011.
Artigo em Russo | MEDLINE | ID: mdl-22117434

RESUMO

The basic principles of the design of direct multiparticle models and the results of multiparticle computer simulation of electron transfer by mobile protein carriers in the photosynthetic membrane of a chloroplast thylakoid are presented. The reactions of complex formation of the protein plastocyanin with the protein cytochrome f and the pigment-protein complex of photosystem I, as well as of the protein ferredoxin with the protein FNR and photosystem 1 are considered. The role of diffusion and electrostatic interactions is discussed, and the effect of the shape of the reaction volume and ionic strength on the rate of electron transport are discussed.


Assuntos
Simulação por Computador , Citocromos f/química , Ferredoxinas/química , Modelos Biológicos , Complexo de Proteína do Fotossistema I/química , Tilacoides/química , Transporte de Elétrons , Ferredoxina-NADP Redutase/química , Plastocianina/química , Ligação Proteica , Eletricidade Estática
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