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Pesquisa : B03.440.623.700 [Categoria DeCS]
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Id: biblio-1045580
Autor: Alleyne, T; Ashe, D.
Título: Hydrogen/rydride ion relay - a mechanism for early electron transfer in cytochrome c oxidases / El reléuónico hidrógeno-hidruro: un mecanismo de transferencia temprana de electrones en las citocromo c oxidasas
Fonte: West Indian med. j;62(1):3-11, Jan. 2013. ilus, tab.
Idioma: en.
Resumo: Cytochrome c oxidase (COX) employs electrons obtained from cytochrome c to bring about the reduction of oxygen to water. It is known that the electrons originate from the haem edge of cytochrome c and enters bovine COX at Trp-104. It is also known that Tyr-105, Glu-198 and Asp-158 of COX subunit II play roles in the enzyme's catalysis but how these roles are linked to electron transfer remain unclear. Recently, we proposed that electrons travel from the haem edge of cytochrome c to CuA, the first metal redox centre of COX, by a hydrogen/hydride ion relay using six residues. Now using a similar computer assisted approach, we investigate the extent to which this hydride/hydrogen ion mechanism is common amongst oxidases. The crystal structures of COX from P denitrificans, R sphaeroides and T thermophilus and quinol oxidase from E coli were downloaded and their binding domains analysed. As with bovine, all four oxidases had only nine amino acid residues in that region and both the sequences and three-dimensional structures were highly conserved. We propose that these residues function as a hydrogen/hydride ion relay, participating directly in electron transfer to CuA. We further suggest that this electron transfer mechanism might be a common feature in oxidases.

La citocromo c oxidasa (COX) emplea electrones obtenidos del citocromo c para producir la reducción del oxígeno a agua. Se sabe que los electrones originan a partir del hemo del citocromo c, y entran en la COX bovina en Trp-104. También se conoce que Tyr-105, Glu-198 y Asp-158 de la subunidad II de COX, desempeñan papeles en la catálisis de la enzima, pero no hay todavía claridad en cuanto a cómo estos papeles se hallan vinculados con la transferencia de electrones. Recientemente, sugerimos que los electrones viajan del borde del hemo del citocromo c al CuA, el primer centro metálico de reacción redox de la COX, por un relé iónico hidrógeno-hidruro, usando seis residuos. Ahora, usando un enfoque similar computarizado, investigamos hasta que punto este mecanismo de iones hidrógeno/hidruro es común entre las oxidasas. Se bajaron y analizaron los dominios de unión de las estructuras cristalinas de la COX de P denitrificans, R sphaeroides, y T thermophilus, y de la quinol oxidasa de la E coli. Como en el caso de la bovina, las cuatro oxidasas tenían sólo nueve residuos de aminoácido en esa región, y tanto las secuencias como las estructuras tridimensionales presentaban un alto grado de conservación. Proponemos que estos residuos funcionan como un relé iónico hidrógeno-hidruro, participando directamente en una transferencia de electrones al CuA. Asimismo, sugerimos que este mecanismo de transferencia de electrones podría ser un rasgo común de las oxidasas.
Descritores: Complexo IV da Cadeia de Transporte de Elétrons/metabolismo
Citocromos c/metabolismo
Paracoccus denitrificans/enzimologia
Rhodobacter sphaeroides/enzimologia
Sequência de Aminoácidos
Thermus thermophilus/enzimologia
Escherichia coli/enzimologia
Limites: Animais
Responsável: BR1.1 - BIREME

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Texto completo SciELO Chile
Texto completo
Id: lil-640497
Autor: Panwichian, Saijai; Kantachote, Duangporn; Wittayaweerasak, Banjong; Mallavarapu, Megharaj.
Título: Removal of heavy metals by exopolymeric substances produced by resistant purple nonsulfur bacteria isolated from contaminated shrimp ponds
Fonte: Electron. j. biotechnol;14(4):2-2, July 2011. ilus, tab.
Idioma: en.
Projeto: Price of Songkla University.
Resumo: Two purple nonsulfur bacteria (PNSB) strains, Rhodobium marinum NW16 and Rhodobacter sphaeroides KMS24 were investigated for their potential to remove heavy metals (HMs) from contaminated shrimp pond water. Tolerance of both PNSB strains growing with both microaerobic-light and aerobic-dark conditions, based on their minimum inhibitory concentrations, was in the order of Cu2+ > Zn2+ > Cd2+ (Pb precipitation occurred at 0.34 mM). Results from a scanning electron microscope equipped with an energy dispersive X-ray spectrometer (SEM-EDX) indicated that Cu2+ and Zn2+ altered the cellular morphology of both strains and accumulated HMs were found in their cells. The highest amounts of both cations were found in their cell walls followed by the cytoplasm and cell membrane. Using the highest concentrations (mM) of HMs found in shrimp pond of 0.0067 Cd2+, 0.54 Cu2+, 0.30 Pb2+, 0.89 Zn2+ and 3 percent NaCl under both incubating conditions exopolymeric substances (EPS) produced by both strains showed a greater removal of all HMs (average percentages; 90.52-97.29) than their cells (average percentages; 14.02-75.03).
Descritores: Aquicultura
Poluição Ambiental
Metais Pesados/metabolismo
-Biodegradação Ambiental
Testes de Sensibilidade Microbiana
Rhodobacter sphaeroides
Responsável: CL1.1 - Biblioteca Central

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Texto completo SciELO Chile
Texto completo
Id: lil-531890
Autor: Sangkharak, Kanokphorn; Prasertsan, Poonsuk.
Título: Nutrient optimization for production of polyhydroxybutyrate from halotolerant photosynthetic bacteria cultivated under aerobic-dark condition
Fonte: Electron. j. biotechnol;11(3):83-94, July 2008. ilus, graf, tab.
Idioma: en.
Resumo: Three halotolerant bacterial strains; Rhodobacter sphaeroides ES16 (the wild type) and the two mutant strains of R. sphaeroides ES16, namely N20 and U7, were cultivated in glutamate-malate (GM) medium and screened for production of polyhydroxybutyrate (PHB). The mutant strains N20 and U7 were found to accumulate PHB (53.9 and 42.0 percent of DCW, respectively) 3.6 and 2.8 times higher than the wild type strain (19.5 percent of DCW), respectively. R. sphaeroides N20 were selected for studies on the effects of nutrient and environmental conditions on PHB accumulation. The optimal condition was 4 g/l acetate, 0.02 g/l (NH4)2SO4, C/N ratio of 6:1, 1.0 g/l K2HPO4, 1.0 g/l KH2PO4 and 3 percent NaCl with initial pH at 7.0. Under this optimal condition, the maximum PHB accumulation increased from 53.9 percent to 88 percent of DCW and 9.11 ± 0.08 g/l biomass, 8.02 +/- 0.10 g/l PHB concentration were achieved after 60 hrs cultivation at 37ºC. These results are the highest values ever obtained from photosynthetic bacteria reported so far.
Descritores: Bactérias Gram-Negativas Fotossintetizantes Oxigênicas
Rhodobacter sphaeroides/enzimologia
Rhodobacter sphaeroides/metabolismo
-Cromatografia Gasosa
Microscopia Eletrônica de Transmissão
Nitrogênio/administração & dosagem
Responsável: CL1.1 - Biblioteca Central

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Texto completo SciELO Brasil
Texto completo
Id: lil-405531
Autor: Braun, P; Gebhardt, R; Kwa, L; Doster, W.
Título: High pressure near infrared study of the mutated light-harvesting complex LH2
Fonte: Braz. j. med. biol. res = Rev. bras. pesqui. méd. biol;38(8):1273-1278, Aug. 2005. ilus, graf.
Idioma: en.
Conferência: Apresentado em: International Conference on High Pressure Bioscience and Biotechnology, 3, Rio de Janeiro, Sept. 26-30, 2004.
Resumo: The pressure sensitivities of the near infrared spectra of the light-harvesting (LH2) complex and a mutant complex with a simplified BChl-B850 binding pocket were compared. In the mutant an abrupt change in the spectral properties occurred at 250 MPa, which was not observed with the native sample. Increased disorder due to collapse of the chromophore pocket is suggested.
Descritores: Escherichia coli/genética
Pressão Hidrostática
Complexos de Proteínas Captadores de Luz/genética
Rhodobacter sphaeroides/genética
Espectroscopia de Luz Próxima ao Infravermelho
-Complexos de Proteínas Captadores de Luz/química
Modelos Moleculares
Responsável: BR1.1 - BIREME

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