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  1 / 3176 MEDLINE  
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[PMID]:29311621
[Au] Autor:Rätsep M; Muru R; Freiberg A
[Ad] Endereço:Institute of Physics, University of Tartu, W. Ostwald Str. 1, 50411, Tartu, Estonia.
[Ti] Título:High temperature limit of photosynthetic excitons.
[So] Source:Nat Commun;9(1):99, 2018 01 08.
[Is] ISSN:2041-1723
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:Excitons in light-harvesting complexes are known to significantly improve solar-energy harnessing. Here we demonstrate photosynthetic excitons at super-physiological temperatures reaching 60-80 °C in different species of mesophilic photosynthetic bacteria. It is shown that the survival of light-harvesting excitons in the peripheral LH2 antennae is restricted by thermal decomposition of the pigment-protein complex rather than by any intrinsic property of excitons. The regular spatial organization of the bacteriochlorophyll a pigments supporting excitons in this complex is lost upon the temperature-induced breakdown of its tertiary structure. Secondary structures of the complexes survive even higher temperatures. The discovered pivotal role of the protein scaffold in the stabilization of excitons comprises an important aspect of structure-function relationship in biology. These results also intimately entangle the fundamental issues of quantum mechanical concepts in biology and in the folding of proteins.
[Mh] Termos MeSH primário: Temperatura Alta
Complexos de Proteínas Captadores de Luz/metabolismo
Fotossíntese
Rhodobacter sphaeroides/metabolismo
[Mh] Termos MeSH secundário: Dicroísmo Circular
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T
[Nm] Nome de substância:
0 (Light-Harvesting Protein Complexes)
[Em] Mês de entrada:1802
[Cu] Atualização por classe:180212
[Lr] Data última revisão:
180212
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:180110
[St] Status:MEDLINE
[do] DOI:10.1038/s41467-017-02544-7


  2 / 3176 MEDLINE  
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[PMID]:28941458
[Au] Autor:Yakovlev AG; Shuvalov VA
[Ad] Endereço:Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia. yakov@genebee.msu.su.
[Ti] Título:Femtosecond Relaxation Processes in Rhodobacter sphaeroides Reaction Centers.
[So] Source:Biochemistry (Mosc);82(8):906-915, 2017 Aug.
[Is] ISSN:1608-3040
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Energy relaxation was studied with difference femtosecond spectroscopy in reaction centers of the YM210L mutant of the purple photosynthetic bacterium Rhodobacter sphaeroides at low temperature (90 K). A dynamical long-wavelength shift of stimulated emission of the excited state of the bacteriochlorophyll dimer P was found, which starts simultaneously with P* formation and is accompanied by a change in the spectral shape of this emission. The characteristic value of this shift was about 30 nm, and the characteristic time about 200 fs. Difference kinetics ΔA measured at fixed wavelengths demonstrate the femtosecond shift of the P* stimulated emission appearing as a dependence of these kinetics on wavelength. We found that the reported long-wavelength shift can be explained in terms of electron-vibrational relaxation of the P* excited state with time constants of vibrational and electronic relaxation of 100 and 50 fs, respectively. Alternative mechanisms of the dynamical shift of the P* stimulated emission spectrum are also discussed in terms of energy redistribution between vibrational modes or coherent excitation of the modes.
[Mh] Termos MeSH primário: Proteínas de Bactérias/metabolismo
Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo
Rhodobacter sphaeroides/metabolismo
[Mh] Termos MeSH secundário: Proteínas de Bactérias/genética
Bacterioclorofilas/química
Bacterioclorofilas/metabolismo
Dimerização
Cinética
Lasers de Estado Sólido
Mutagênese Sítio-Dirigida
Complexo de Proteínas do Centro de Reação Fotossintética/genética
Rhodobacter sphaeroides/efeitos da radiação
Espectrofotometria
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Bacterial Proteins); 0 (Bacteriochlorophylls); 0 (Photosynthetic Reaction Center Complex Proteins)
[Em] Mês de entrada:1710
[Cu] Atualização por classe:171025
[Lr] Data última revisão:
171025
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170925
[St] Status:MEDLINE
[do] DOI:10.1134/S0006297917080053


  3 / 3176 MEDLINE  
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[PMID]:28803776
[Au] Autor:Bhat JY; Milicic G; Thieulin-Pardo G; Bracher A; Maxwell A; Ciniawsky S; Mueller-Cajar O; Engen JR; Hartl FU; Wendler P; Hayer-Hartl M
[Ad] Endereço:Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
[Ti] Título:Mechanism of Enzyme Repair by the AAA Chaperone Rubisco Activase.
[So] Source:Mol Cell;67(5):744-756.e6, 2017 Sep 07.
[Is] ISSN:1097-4164
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:How AAA+ chaperones conformationally remodel specific target proteins in an ATP-dependent manner is not well understood. Here, we investigated the mechanism of the AAA+ protein Rubisco activase (Rca) in metabolic repair of the photosynthetic enzyme Rubisco, a complex of eight large (RbcL) and eight small (RbcS) subunits containing eight catalytic sites. Rubisco is prone to inhibition by tight-binding sugar phosphates, whose removal is catalyzed by Rca. We engineered a stable Rca hexamer ring and analyzed its functional interaction with Rubisco. Hydrogen/deuterium exchange and chemical crosslinking showed that Rca structurally destabilizes elements of the Rubisco active site with remarkable selectivity. Cryo-electron microscopy revealed that Rca docks onto Rubisco over one active site at a time, positioning the C-terminal strand of RbcL, which stabilizes the catalytic center, for access to the Rca hexamer pore. The pulling force of Rca is fine-tuned to avoid global destabilization and allow for precise enzyme repair.
[Mh] Termos MeSH primário: Proteínas de Bactérias/metabolismo
Chaperonas Moleculares/metabolismo
Proteínas de Plantas/metabolismo
Rhodobacter sphaeroides/enzimologia
Ribulose-Bifosfato Carboxilase/metabolismo
Ativador de Plasminogênio Tecidual/metabolismo
[Mh] Termos MeSH secundário: Trifosfato de Adenosina/metabolismo
Regulação Alostérica
Proteínas de Bactérias/química
Proteínas de Bactérias/genética
Sítios de Ligação
Domínio Catalítico
Reagentes para Ligações Cruzadas/química
Medição da Troca de Deutério
Estabilidade Enzimática
Chaperonas Moleculares/química
Chaperonas Moleculares/genética
Simulação de Acoplamento Molecular
Ligação Proteica
Domínios e Motivos de Interação entre Proteínas
Estrutura Quaternária de Proteína
Subunidades Proteicas
Rhodobacter sphaeroides/genética
Ribulose-Bifosfato Carboxilase/química
Ribulose-Bifosfato Carboxilase/genética
Relação Estrutura-Atividade
Fatores de Tempo
Ativador de Plasminogênio Tecidual/química
Ativador de Plasminogênio Tecidual/genética
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Bacterial Proteins); 0 (Cross-Linking Reagents); 0 (Molecular Chaperones); 0 (Plant Proteins); 0 (Protein Subunits); 0 (rca protein, plant); 8L70Q75FXE (Adenosine Triphosphate); EC 3.4.21.68 (Tissue Plasminogen Activator); EC 4.1.1.39 (Ribulose-Bisphosphate Carboxylase)
[Em] Mês de entrada:1709
[Cu] Atualização por classe:170925
[Lr] Data última revisão:
170925
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170815
[St] Status:MEDLINE


  4 / 3176 MEDLINE  
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[PMID]:28739674
[Au] Autor:Jones CW; Armitage JP
[Ad] Endereço:Department of Biochemistry, University of Oxford, Oxford, United Kingdom.
[Ti] Título:Essential Role of the Cytoplasmic Chemoreceptor TlpT in the Formation of Chemosensory Complexes in Rhodobacter sphaeroides.
[So] Source:J Bacteriol;199(19), 2017 Oct 01.
[Is] ISSN:1098-5530
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Bacterial chemosensory proteins form large hexagonal arrays. Several key features of chemotactic signaling depend on these large arrays, namely, cooperativity between receptors, sensitivity, integration of different signals, and adaptation. The best-studied arrays are the membrane-associated arrays found in most bacteria. has two spatially distinct chemosensory arrays, one is transmembrane and the other is cytoplasmic. These two arrays work together to control a single flagellum. Deletion of one of the soluble chemoreceptors, TlpT, results in the loss of the formation of the cytoplasmic array. Here, we show the expression of TlpT in a deletion background results in the reformation of the cytoplasmic array. The number of arrays formed is dependent on the cell length, indicating spatial limitations on the number of arrays in a cell and stochastic assembly. Deletion of PpfA, a protein required for the positioning and segregation of the cytoplasmic array, results in slower array formation upon TlpT expression and fewer arrays, suggesting it accelerates cluster assembly. Bacterial chemosensory arrays are usually membrane associated and consist of thousands of copies of receptors, adaptor proteins, kinases, and adaptation enzymes packed into large hexagonal structures. also has cytoplasmic arrays, which divide and segregate using a chromosome-associated ATPase, PpfA. The expression of the soluble chemoreceptor TlpT is shown to drive the formation of the arrays, accelerated by PpfA. The positioning of these arrays suggests their position is the result of stochastic assembly rather than active positioning.
[Mh] Termos MeSH primário: Proteínas de Bactérias/metabolismo
Citoplasma/metabolismo
Proteínas de Membrana/metabolismo
Rhodobacter sphaeroides/metabolismo
[Mh] Termos MeSH secundário: Proteínas de Bactérias/genética
Quimiotaxia
Proteínas de Membrana/genética
Rhodobacter sphaeroides/genética
Transdução de Sinais
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Bacterial Proteins); 0 (Membrane Proteins)
[Em] Mês de entrada:1710
[Cu] Atualização por classe:171003
[Lr] Data última revisão:
171003
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170726
[St] Status:MEDLINE


  5 / 3176 MEDLINE  
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[PMID]:28688734
[Au] Autor:Altamura E; Fiorentino R; Milano F; Trotta M; Palazzo G; Stano P; Mavelli F
[Ad] Endereço:Chemistry Department, University "Aldo Moro", Via Orabona 4, I-70126 Bari, Italy.
[Ti] Título:First moves towards photoautotrophic synthetic cells: In vitro study of photosynthetic reaction centre and cytochrome bc1 complex interactions.
[So] Source:Biophys Chem;229:46-56, 2017 Oct.
[Is] ISSN:1873-4200
[Cp] País de publicação:Netherlands
[La] Idioma:eng
[Ab] Resumo:Following a bottom-up synthetic biology approach it is shown that vesicle-based cell-like systems (shortly "synthetic cells") can be designed and assembled to perform specific function (for biotechnological applications) and for studies in the origin-of-life field. We recently focused on the construction of synthetic cells capable to converting light into chemical energy. Here we first present our approach, which has been realized so far by the reconstitution of photosynthetic reaction centre in the membrane of giant lipid vesicles. Next, the details of our ongoing research program are presented. It involves the use of the reaction centre, the coenzyme Q-cytochrome c oxidoreductase, and the ATP synthase for creating an autonomous synthetic cell. We show experimental results on the chemistry of the first two proteins showing that they can efficiently sustain light-driven chemical oscillations. Moreover, the cyclic pattern has been reproduced in silico by a minimal kinetic model.
[Mh] Termos MeSH primário: Complexo III da Cadeia de Transporte de Elétrons/metabolismo
Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo
[Mh] Termos MeSH secundário: Sistema Livre de Células
Difusão Dinâmica da Luz
Transporte de Elétrons
Complexo III da Cadeia de Transporte de Elétrons/química
Cinética
Lipossomos/química
Lipossomos/metabolismo
Oxirredução
Fotossíntese
Complexo de Proteínas do Centro de Reação Fotossintética/química
Rhodobacter sphaeroides/metabolismo
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Liposomes); 0 (Photosynthetic Reaction Center Complex Proteins); EC 1.10.2.2 (Electron Transport Complex III)
[Em] Mês de entrada:1710
[Cu] Atualização por classe:171010
[Lr] Data última revisão:
171010
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170710
[St] Status:MEDLINE


  6 / 3176 MEDLINE  
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[PMID]:28657308
[Au] Autor:Saga Y; Hirota K; Asakawa H; Takao K; Fukuma T
[Ad] Endereço:Department of Chemistry, Faculty of Science and Engineering, Kindai University , Higashi-Osaka, Osaka 577-8502, Japan.
[Ti] Título:Reversible Changes in the Structural Features of Photosynthetic Light-Harvesting Complex 2 by Removal and Reconstitution of B800 Bacteriochlorophyll a Pigments.
[So] Source:Biochemistry;56(27):3484-3491, 2017 Jul 11.
[Is] ISSN:1520-4995
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Light-harvesting complex 2 (LH2) is an integral membrane protein in purple photosynthetic bacteria. This protein possesses two types of bacteriochlorophyll (BChl) a, termed B800 and B850, which exhibit lowest-energy absorption bands (Q bands) around 800 and 850 nm. These BChl a pigments in the LH2 protein play crucial roles not only in photosynthetic functions but also in folding and maintaining its protein structure. We report herein the reversible structural changes in the LH2 protein derived from a purple photosynthetic bacterium, Rhodoblastus acidophilus, induced by the removal of B800 BChl a (denoted as B800-free LH2) and the reconstitution of exogenous BChl a. Atomic force microscopy observation clearly visualized the nonameric ring structure of the B800-free LH2 with almost the same diameter as the native LH2. Size exclusion chromatography measurements indicated a considerable decrease in the size of the protein induced by the removal of B800 BChl a. The protein size was almost recovered by the insertion of BChl a pigments into the B800 binding sites. The decrease in the LH2 size would mainly originate from the shrinkage of the B800 binding sites perpendicular to the macrocycle of B800 BChl a without deformation of the circular arrangement. The reversible changes in the LH2 structure induced by the removal and reconstitution of B800 BChl a will be helpful for understanding the structural principle and the folding mechanism of photosynthetic pigment-protein complexes.
[Mh] Termos MeSH primário: Proteínas de Bactérias/metabolismo
Bacterioclorofila A/metabolismo
Complexos de Proteínas Captadores de Luz/metabolismo
Modelos Moleculares
Pigmentos Biológicos/metabolismo
Rhodobacter sphaeroides/metabolismo
Rodopseudomonas/enzimologia
[Mh] Termos MeSH secundário: Proteínas de Bactérias/química
Proteínas de Bactérias/isolamento & purificação
Bacterioclorofila A/química
Bacterioclorofila A/isolamento & purificação
Sítios de Ligação
Cromatografia em Gel
Dicroísmo Circular
Concentração de Íons de Hidrogênio
Complexos de Proteínas Captadores de Luz/química
Complexos de Proteínas Captadores de Luz/isolamento & purificação
Microscopia de Força Atômica
Peso Molecular
Pigmentos Biológicos/química
Pigmentos Biológicos/isolamento & purificação
Conformação Proteica
Dobramento de Proteína
Multimerização Proteica
Estrutura Quaternária de Proteína
Espectrofotometria Ultravioleta
[Pt] Tipo de publicação:COMPARATIVE STUDY; JOURNAL ARTICLE
[Nm] Nome de substância:
0 (B800-850 light-harvesting complex, bacteria); 0 (Bacterial Proteins); 0 (Bacteriochlorophyll A); 0 (Light-Harvesting Protein Complexes); 0 (Pigments, Biological)
[Em] Mês de entrada:1707
[Cu] Atualização por classe:170726
[Lr] Data última revisão:
170726
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170629
[St] Status:MEDLINE
[do] DOI:10.1021/acs.biochem.7b00267


  7 / 3176 MEDLINE  
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[PMID]:28644830
[Au] Autor:Godány M; Khatri BS; Goldstein RA
[Ad] Endereço:Division of Infection & Immunity, University College London, London, United Kingdom.
[Ti] Título:Optimal chemotactic responses in stochastic environments.
[So] Source:PLoS One;12(6):e0179111, 2017.
[Is] ISSN:1932-6203
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:Although the "adaptive" strategy used by Escherichia coli has dominated our understanding of bacterial chemotaxis, the environmental conditions under which this strategy emerged is still poorly understood. In this work, we study the performance of various chemotactic strategies under a range of stochastic time- and space-varying attractant distributions in silico. We describe a novel "speculator" response in which the bacterium compare the current attractant concentration to the long-term average; if it is higher then they tumble persistently, while if it is lower than the average, bacteria swim away in search of more favorable conditions. We demonstrate how this response explains the experimental behavior of aerobically-grown Rhodobacter sphaeroides and that under spatially complex but slowly-changing nutrient conditions the speculator response is as effective as the adaptive strategy of E. coli.
[Mh] Termos MeSH primário: Quimiotaxia/fisiologia
Escherichia coli/fisiologia
Modelos Biológicos
Rhodobacter sphaeroides/fisiologia
[Mh] Termos MeSH secundário: Internet
Software
Processos Estocásticos
Natação/fisiologia
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Em] Mês de entrada:1709
[Cu] Atualização por classe:170920
[Lr] Data última revisão:
170920
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170624
[St] Status:MEDLINE
[do] DOI:10.1371/journal.pone.0179111


  8 / 3176 MEDLINE  
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[PMID]:28617267
[Au] Autor:Li X; Peng W; Jia Y; Lu L; Fan W
[Ad] Endereço:School of Space and Environment, Beihang University, No. 37 Xueyuan Road, Haidian District, Beijing 100191, China E-mail: fanwh@buaa.edu.cn.
[Ti] Título:Removal of cadmium and zinc from contaminated wastewater using Rhodobacter sphaeroides.
[So] Source:Water Sci Technol;75(11-12):2489-2498, 2017 Jun.
[Is] ISSN:0273-1223
[Cp] País de publicação:England
[La] Idioma:eng
[Ab] Resumo:Rhodobacter sphaeroides was used for bioremediation of wastewater polluted with cadmium (Cd) and zinc (Zn). The tolerance of the microorganism to selected heavy metals (HMs), as well as the effects of pH, temperature and inoculum size on the removal rate, was investigated. The remediation effects of R. sphaeroides were analysed at different initial concentrations of HMs. Bioremediation mechanisms were thoroughly discussed based on the results from the cell characterisation analysis. Cd and Zn could inhibit the growth of R. sphaeroides. However, Cd was more toxic than Zn, with corresponding EC values of 5.34 and 69.79 mg L . Temperature and pH had greater influence on the removal rate of HMs than inoculum size. The optimal conditions for temperature and pH were 35 °C-40 °C and pH 7, respectively. Initial concentration of HMs and remediation time also affected the removal rate. Rhodobacter sphaeroides had a relatively higher remediation effect under the present experimental conditions. The removal rates for Cd and Zn reached 97.92% and 97.76%, respectively. Results showed that biosorption and HM precipitation were the main bioremediation mechanisms. This information is necessary to better understand the removal mechanism of R. sphaeroides, and is significant for its pilot test and future practical application.
[Mh] Termos MeSH primário: Cádmio/metabolismo
Rhodobacter sphaeroides/crescimento & desenvolvimento
Rhodobacter sphaeroides/metabolismo
Águas Residuais/análise
Poluentes Químicos da Água/metabolismo
Zinco/metabolismo
[Mh] Termos MeSH secundário: Biodegradação Ambiental
Microscopia Eletrônica de Varredura
Espectroscopia de Infravermelho com Transformada de Fourier
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Waste Water); 0 (Water Pollutants, Chemical); 00BH33GNGH (Cadmium); J41CSQ7QDS (Zinc)
[Em] Mês de entrada:1708
[Cu] Atualização por classe:170817
[Lr] Data última revisão:
170817
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170616
[St] Status:MEDLINE
[do] DOI:10.2166/wst.2016.608


  9 / 3176 MEDLINE  
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[PMID]:28601078
[Au] Autor:Khatypov RA; Khristin AM; Fufina TY; Shuvalov VA
[Ad] Endereço:Institute of Basic Biological Problems, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia. rgreen1@rambler.ru.
[Ti] Título:An Alternative Pathway of Light-Induced Transmembrane Electron Transfer in Photosynthetic Reaction Centers of Rhodobacter sphaeroides.
[So] Source:Biochemistry (Mosc);82(6):692-697, 2017 Jun.
[Is] ISSN:1608-3040
[Cp] País de publicação:United States
[La] Idioma:eng
[Ab] Resumo:In the absorption spectrum of Rhodobacter sphaeroides reaction centers, a minor absorption band was found with a maximum at 1053 nm. The amplitude of this band is ~10,000 times less and its half-width is comparable to that of the long-wavelength absorption band of the primary electron donor P . When the primary electron donor is excited by femtosecond light pulses at 870 nm, the absorption band at 1053 nm is increased manifold during the earliest stages of charge separation. The growth of this absorption band in difference absorption spectra precedes the appearance of stimulated emission at 935 nm and the appearance of the absorption band of anion-radical B at 1020 nm, reported earlier by several researchers. When reaction centers are illuminated with 1064 nm light, the absorption spectrum undergoes changes indicating reduction of the primary electron acceptor Q , with the primary electron donor P remaining neutral. These photoinduced absorption changes reflect the formation of the long-lived radical state PB H Q .
[Mh] Termos MeSH primário: Proteínas de Bactérias/metabolismo
Membrana Celular/metabolismo
Fotossíntese/fisiologia
Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo
Rhodobacter sphaeroides/metabolismo
[Mh] Termos MeSH secundário: Transporte de Elétrons/fisiologia
[Pt] Tipo de publicação:JOURNAL ARTICLE
[Nm] Nome de substância:
0 (Bacterial Proteins); 0 (Photosynthetic Reaction Center Complex Proteins)
[Em] Mês de entrada:1706
[Cu] Atualização por classe:170621
[Lr] Data última revisão:
170621
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170612
[St] Status:MEDLINE
[do] DOI:10.1134/S0006297917060050


  10 / 3176 MEDLINE  
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[PMID]:28587931
[Au] Autor:Qian P; Martin EC; Ng IW; Hunter CN
[Ad] Endereço:Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom.
[Ti] Título:The C-terminus of PufX plays a key role in dimerisation and assembly of the reaction center light-harvesting 1 complex from Rhodobacter sphaeroides.
[So] Source:Biochim Biophys Acta;1858(9):795-803, 2017 09.
[Is] ISSN:0006-3002
[Cp] País de publicação:Netherlands
[La] Idioma:eng
[Ab] Resumo:In bacterial photosynthesis reaction center-light-harvesting 1 (RC-LH1) complexes trap absorbed solar energy by generating a charge separated state. Subsequent electron and proton transfers form a quinol, destined to diffuse to the cytochrome bc complex. In bacteria such as Rhodobacter (Rba.) sphaeroides and Rba. capsulatus the PufX polypeptide creates a channel for quinone/quinol traffic across the LH1 complex that surrounds the RC, and it is therefore essential for photosynthetic growth. PufX also plays a key role in dimerization of the RC-LH1-PufX core complex, and the structure of the Rba. sphaeroides complex shows that the PufX C-terminus, particularly the region from X49-X53, likely mediates association of core monomers. To investigate this putative interaction we analysed mutations PufX R49L, PufX R53L, PufX R49/53L and PufX G52L by measuring photosynthetic growth, fractionation of detergent-solubilised membranes, formation of 2-D crystals and electron microscopy. We show that these mutations do not affect assembly of PufX within the core or photosynthetic growth but they do prevent dimerization, consistent with predictions from the RC-LH1-PufX structure. We obtained low resolution structures of monomeric core complexes with and without PufX, using electron microscopy of negatively stained single particles and 3D reconstruction; the monomeric complex with PufX corresponds to one half of the dimer structure whereas LH1 completely encloses the RC if the gene encoding PufX is deleted. On the basis of the insights gained from these mutagenesis and structural analyses we propose a sequence for assembly of the dimeric RC-LH1-PufX complex.
[Mh] Termos MeSH primário: Proteínas de Bactérias/fisiologia
Complexos de Proteínas Captadores de Luz/química
Rhodobacter sphaeroides/metabolismo
[Mh] Termos MeSH secundário: Sequência de Aminoácidos
Substituição de Aminoácidos
Proteínas de Bactérias/química
Proteínas de Bactérias/genética
Proteínas de Bactérias/ultraestrutura
Benzoquinonas/metabolismo
Cristalização
Dimerização
Hidroquinonas/metabolismo
Processamento de Imagem Assistida por Computador
Complexos de Proteínas Captadores de Luz/genética
Complexos de Proteínas Captadores de Luz/fisiologia
Complexos de Proteínas Captadores de Luz/ultraestrutura
Microscopia Eletrônica
Modelos Moleculares
Mutação de Sentido Incorreto
Mutação Puntual
Conformação Proteica
Domínios Proteicos
Rhodobacter sphaeroides/genética
Rhodobacter sphaeroides/efeitos da radiação
[Pt] Tipo de publicação:JOURNAL ARTICLE; RESEARCH SUPPORT, NON-U.S. GOV'T; RESEARCH SUPPORT, U.S. GOV'T, NON-P.H.S.
[Nm] Nome de substância:
0 (Bacterial Proteins); 0 (Benzoquinones); 0 (Hydroquinones); 0 (Light-Harvesting Protein Complexes); 0 (PufX protein, Rhodobacter); 3T006GV98U (quinone)
[Em] Mês de entrada:1710
[Cu] Atualização por classe:171025
[Lr] Data última revisão:
171025
[Sb] Subgrupo de revista:IM
[Da] Data de entrada para processamento:170608
[St] Status:MEDLINE



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