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1.
Front Microbiol ; 14: 1253114, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37860142

RESUMO

The recent reclassification of the strict anaerobe Geobacter sulfurreducens bacterium as aerotolerant brought attention for oxidative stress protection pathways. Although the electron transfer pathways for oxygen detoxification are not well established, evidence was obtained for the formation of a redox complex between the periplasmic triheme cytochrome PpcA and the diheme cytochrome peroxidase MacA. In the latter, the reduction of the high-potential heme triggers a conformational change that displaces the axial histidine of the low-potential heme with peroxidase activity. More recently, a possible involvement of the triheme periplasmic cytochrome family (PpcA-E) in the protection from oxidative stress in G. sulfurreducens was suggested. To evaluate this hypothesis, we investigated the electron transfer reaction and the biomolecular interaction between each PpcA-E cytochrome and MacA. Using a newly developed method that relies on the different NMR spectral signatures of the heme proteins, we directly monitored the electron transfer reaction from reduced PpcA-E cytochromes to oxidized MacA. The results obtained showed a complete electron transfer from the cytochromes to the high-potential heme of MacA. This highlights PpcA-E cytochromes' efficient role in providing the necessary reducing power to mitigate oxidative stress situations, hence contributing to a better knowledge of oxidative stress protection pathways in G. sulfurreducens.

2.
J Biol Chem ; 299(10): 105167, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37595873

RESUMO

Microbial extracellular reduction of insoluble compounds requires soluble electron shuttles that diffuse in the environment, freely diffusing cytochromes, or direct contact with cellular conductive appendages that release or harvest electrons to assure a continuous balance between cellular requirements and environmental conditions. In this work, we produced and characterized the three cytochrome domains of PgcA, an extracellular triheme cytochrome that contributes to Fe(III) and Mn(IV) oxides reduction in Geobacter sulfurreducens. The three monoheme domains are structurally homologous, but their heme groups show variable axial coordination and reduction potential values. Electron transfer experiments monitored by NMR and visible spectroscopy show the variable extent to which the domains promiscuously exchange electrons while reducing different electron acceptors. The results suggest that PgcA is part of a new class of cytochromes - microbial heme-tethered redox strings - that use low-complexity protein stretches to bind metals and promote intra- and intermolecular electron transfer events through its cytochrome domains.

3.
Int J Mol Sci ; 24(8)2023 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-37108196

RESUMO

Periplasmic nanowires and electric conductive filaments made of the polymeric assembly of c-type cytochromes from Geobacter sulfurreducens bacterium are crucial for electron storage and/or extracellular electron transfer. The elucidation of the redox properties of each heme is fundamental to the understanding of the electron transfer mechanisms in these systems, which first requires the specific assignment of the heme NMR signals. The high number of hemes and the molecular weight of the nanowires dramatically decrease the spectral resolution and make this assignment extremely complex or unattainable. The nanowire cytochrome GSU1996 (~42 kDa) is composed of four domains (A to D) each containing three c-type heme groups. In this work, the individual domains (A to D), bi-domains (AB, CD) and full-length nanowire were separately produced at natural abundance. Sufficient protein expression was obtained for domains C (~11 kDa/three hemes) and D (~10 kDa/three hemes), as well as for bi-domain CD (~21 kDa/six hemes). Using 2D-NMR experiments, the assignment of the heme proton NMR signals for domains C and D was obtained and then used to guide the assignment of the corresponding signals in the hexaheme bi-domain CD. This new biochemical deconstruction-based procedure, using nanowire GSU1996 as a model, establishes a new strategy to functionally characterize large multiheme cytochromes.


Assuntos
Proteínas de Bactérias , Geobacter , Proteínas de Bactérias/metabolismo , Oxirredução , Citocromos/metabolismo , Transporte de Elétrons , Geobacter/metabolismo , Heme/metabolismo
4.
Chemistry ; 28(66): e202202333, 2022 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-36037397

RESUMO

Electron harvesting bacteria are key targets to develop microbial electrosynthesis technologies, which are valid alternatives for the production of value-added compounds without utilization of fossil fuels. Geobacter sulfurreducens, that is capable of donating and accepting electrons from electrodes, is one of the most promising electroactive bacteria. Its electron transfer mechanisms to electrodes have been progressively elucidated, however the electron harvesting pathways are still poorly understood. Previous studies showed that the periplasmic cytochromes PccH and GSU2515 are overexpressed in current-consuming G. sulfurreducens biofilms. PccH was characterized, though no putative partners have been identified. In this work, GSU2515 was characterized by complementary biophysical techniques and in silico simulations using the AlphaFold neural network. GSU2515 is a low-spin monoheme cytochrome with a disordered N-terminal region and an α-helical C-terminal domain harboring the heme group. The cytochrome undergoes a redox-linked heme axial ligand switch, with Met91 and His94 as distal axial ligands in the reduced and oxidized states, respectively. The reduction potential of the cytochrome is negative and modulated by the pH in the physiological range: -78 mV at pH 6 and -113 mV at pH 7. Such pH-dependence coupled to the redox-linked switch of the axial ligand allows the cytochrome to drive a proton-coupled electron transfer step that is crucial to confer directionality to the respiratory chain. Biomolecular interactions and electron transfer experiments indicated that GSU2515 and PccH form a redox complex. Overall, the data obtained highlight for the first time how periplasmic proteins bridge the electron transfer between the outer and inner membrane in the electron harvesting pathways of G. sulfurreducens.


Assuntos
Proteínas de Bactérias , Elétrons , Ligantes , Proteínas de Bactérias/metabolismo , Citocromos/química , Citocromos/metabolismo , Heme/química , Transporte de Elétrons , Oxirredução
5.
Front Microbiol ; 13: 898015, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35620088

RESUMO

Exoelectrogenic microorganisms are in the spotlight due to their unique respiratory mechanisms and potential applications in distinct biotechnological fields, including bioremediation, bioenergy production and microbial electrosynthesis. These applications rely on the capability of these microorganisms to perform extracellular electron transfer, a mechanism that allows the bacteria to transfer electrons to the cell's exterior by establishing functional interfaces between different multiheme cytochromes at the inner membrane, periplasmic space, and outer membrane. The multiheme cytochrome CbcL from Geobacter sulfurreducens is associated to the inner membrane and plays an essential role in the transfer of electrons to final electron acceptors with a low redox potential, as Fe(III) oxides and electrodes poised at -100 mV. CbcL has a transmembranar di-heme b-type cytochrome domain with six helices, linked to a periplasmic cytochrome domain with nine c-type heme groups. The complementary usage of ultraviolet-visible, circular dichroism and nuclear magnetic resonance permitted the structural and functional characterization of CbcL's periplasmic domain. The protein was found to have a high percentage of disordered regions and its nine hemes are low-spin and all coordinated by two histidine residues. The apparent midpoint reduction potential of the CbcL periplasmic domain was determined, suggesting a thermodynamically favorable transfer of electrons to the putative redox partner in the periplasm - the triheme cytochrome PpcA. The establishment of a redox complex between the two proteins was confirmed by probing the electron transfer reaction and the molecular interactions between CbcL and PpcA. The results obtained show for the first time how electrons are injected into the periplasm of Geobacter sulfurreducens for subsequent transfer to the cell's exterior.

6.
Cell Mol Gastroenterol Hepatol ; 13(2): 351-367, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-34454168

RESUMO

The intestinal epithelium has one of the highest turnover rates in the human body, which is supported by intestinal stem cells. Culture models of intestinal physiology have been evolving to incorporate different tissue and microenvironmental elements. However, these models also display gaps that limit their similarity with native conditions. Microfluidics technology arose from the application of microfabrication techniques to fluid manipulation. Recently, microfluidic approaches have been coupled with cell culture, creating self-contained and modular in vitro models with easily controllable features named organs-on-chip. Intestine-on-chip models have enabled the recreation of the proliferative and differentiated compartments of the intestinal epithelium, the long-term maintenance of commensals, and the intraluminal perfusion of organoids. In addition, studies based on human primary intestinal cells have shown that these systems have a closer transcriptomic profile and functionality to the intestine in vivo, when compared with other in vitro models. The design flexibility inherent to microfluidic technology allows the simultaneous combination of components such as shear stress, peristalsis-like strain, 3-dimensional structure, oxygen gradient, and co-cultures with other important cell types involved in gut physiology. The versatility and complexity of the intestine-on-chip grants it the potential for applications in disease modeling, host-microbiota studies, stem cell biology, and, ultimately, the translation to the pharmaceutical industry and the clinic as a reliable high-throughput platform for drug testing and personalized medicine, respectively. This review focuses on the physiological importance of several components that have been incorporated into intestine-on-chip models and highlights interesting features developed in other types of in vitro models that might contribute to the refinement of these systems.


Assuntos
Dispositivos Lab-On-A-Chip , Organoides , Técnicas de Cultura de Células , Técnicas de Cocultura , Humanos , Microfluídica
7.
Int J Mol Sci ; 22(16)2021 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-34445739

RESUMO

Environmental changes trigger the continuous adaptation of bacteria to ensure their survival. This is possible through a variety of signal transduction pathways involving chemoreceptors known as methyl-accepting chemotaxis proteins (MCP) that allow the microorganisms to redirect their mobility towards favorable environments. MCP are two-component regulatory (or signal transduction) systems (TCS) formed by a sensor and a response regulator domain. These domains synchronize transient protein phosphorylation and dephosphorylation events to convert the stimuli into an appropriate cellular response. In this review, the variability of TCS domains and the most common signaling mechanisms are highlighted. This is followed by the description of the overall cellular topology, classification and mechanisms of MCP. Finally, the structural and functional properties of a new family of MCP found in Geobacter sulfurreducens are revisited. This bacterium has a diverse repertoire of chemosensory systems, which represents a striking example of a survival mechanism in challenging environments. Two G. sulfurreducens MCP-GSU0582 and GSU0935-are members of a new family of chemotaxis sensor proteins containing a periplasmic PAS-like sensor domain with a c-type heme. Interestingly, the cellular location of this domain opens new routes to the understanding of the redox potential sensing signaling transduction pathways.


Assuntos
Quimiotaxia/fisiologia , Geobacter/fisiologia , Proteínas Quimiotáticas Aceptoras de Metil/fisiologia , Transdução de Sinais
8.
Biochem J ; 478(14): 2871-2887, 2021 07 30.
Artigo em Inglês | MEDLINE | ID: mdl-34190983

RESUMO

The redox potential values of cytochromes can be modulated by the protonation/deprotonation of neighbor groups (redox-Bohr effect), a mechanism that permits the proteins to couple electron/proton transfer. In the respiratory chains, this effect is particularly relevant if observed in the physiological pH range, as it may contribute to the electrochemical gradient for ATP synthesis. A constitutively produced family of five triheme cytochromes (PpcA-E) from the bacterium Geobacter sulfurreducens plays a crucial role in extracellular electron transfer, a hallmark that permits this bacterium to be explored for several biotechnological applications. Two members of this family (PpcA and PpcD) couple electron/proton transfer in the physiological pH range, a feature not shared with PpcB and PpcE. That ability is crucial for G. sulfurreducens' growth in Fe(III)-reducing habitats since extra contributors to the electrochemical gradient are needed. It was postulated that the redox-Bohr effect is determined by the nature of residue 6, a leucine in PpcA/PpcD and a phenylalanine in PpcB/PpcE. To confirm this hypothesis, Phe6 was replaced by leucine in PpcB and PpcE. The functional properties of these mutants were investigated by NMR and UV-visible spectroscopy to assess their capability to couple electron/proton transfer in the physiological pH range. The results obtained showed that the mutants have an increased redox-Bohr effect and are now capable of coupling electron/proton transfer. This confirms the determinant role of the nature of residue 6 in the modulation of the redox-Bohr effect in this family of cytochromes, opening routes to engineer Geobacter cells with improved biomass production.


Assuntos
Proteínas de Bactérias/metabolismo , Citocromos/metabolismo , Geobacter/metabolismo , Heme/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Citocromos/química , Citocromos/genética , Transporte de Elétrons/genética , Elétrons , Geobacter/genética , Heme/química , Concentração de Íons de Hidrogênio , Modelos Moleculares , Estrutura Molecular , Mutação , Oxirredução , Conformação Proteica , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Prótons , Espectrofotometria/métodos , Termodinâmica
9.
J Biol Chem ; 296: 100711, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33915126

RESUMO

Geobacter bacteria are able to transfer electrons to the exterior of the cell and reduce extracellular electron acceptors including toxic/radioactive metals and electrode surfaces, with potential applications in bioremediation or electricity harvesting. The triheme c-type cytochrome PpcA from Geobacter metallireducens plays a crucial role in bridging the electron transfer from the inner to the outer membrane, ensuring an effective extracellular electron transfer. This cytochrome shares 80% identity with PpcA from Geobacter sulfurreducens, but their redox properties are markedly different, thus determining the distinctive working redox potential ranges in the two bacteria. PpcA from G. metallireducens possesses two extra aromatic amino acids (Phe-6 and Trp-45) in its hydrophobic heme core, whereas PpcA from G. sulfurreducens has a leucine and a methionine in the equivalent positions. Given the different nature of these residues in the two cytochromes, we have hypothesized that the extra aromatic amino acids could be partially responsible for the observed functional differences. In this work, we have replaced Phe-6 and Trp-45 residues by their nonaromatic counterparts in PpcA from G. sulfurreducens. Using redox titrations followed by UV-visible and NMR spectroscopy we observed that residue Trp-45 shifted the redox potential range 33% toward that of PpcA from G. sulfurreducens, whereas Phe-6 produced a negligible effect. For the first time, it is shown that the inclusion of an aromatic residue at the heme core can modulate the working redox range in abundant periplasmic proteins, paving the way to engineer bacterial strains for optimal microbial bioelectrochemical applications.


Assuntos
Citocromos/química , Citocromos/metabolismo , Geobacter/citologia , Geobacter/enzimologia , Heme , Periplasma/enzimologia , Interações Hidrofóbicas e Hidrofílicas , Cinética , Modelos Moleculares , Oxirredução , Domínios Proteicos
10.
Int J Surg Case Rep ; 71: 120-125, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32446990

RESUMO

INTRODUCTION: Posterior retroperitoneoscopic adrenalectomy (PRA) has advantages over transperitoneal approach. A second group of 10 patients is analyzed and compared with the first 10 procedures. Conclusions on feasibility, safety and learning curve are taken. MATERIAL AND METHODS: A retrospective analysis of a second group of 10 patients submitted to PRA was conducted. All patients with functioning and non-functioning adrenal tumors <6-8 cm and without features of malignancy were included. A comparison with the previous 10 cases was conducted, and the results of all 20 cases were compared with other surgeons. RESULTS: Pre-operative diagnoses: Conn's syndrome - 8 (80%); Pheochromocytoma - 1 (10%); Non-functioning tumor (≥ 4 cm) - 1 (10%). Mean size of adrenal tumors was 2,9 cm. Mean operative time for first group was 46,7 min and 31,1 min for the second (p = 0,036). Postoperative in-hospital days decreased in the second group (p = 0,01). Conversion rate was equal (10%). Morbidity and mortality were similar. DISCUSSION: Comparing the evolution of operative time in both groups, a constant and faster operative time was noted for the second group and a decreasing linear tendency was noted as more cases were being performed. Postoperative in-hospital days lowered in the second group, because with experience we started discharging patients earlier. Outcomes are stable between both groups. Our results match other authors data. CONCLUSION: These results are consistent with our first report and support the small learning curve for PRA, which is technically feasible and safe. Operative time and in-hospital days are influenced by surgeon's experience. More cases need to be collected so that these results can be validated.

11.
Plants (Basel) ; 8(8)2019 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-31366082

RESUMO

Knowledge about folk medicines is limited to elder community members of remote communities, like Sete Cidades in the Azores. The Azores, 1300 km west of Portugal, are nine volcanic islands, totalling 2330 km2 of land dispersed by 173,200 km2 in the North Atlantic Ocean. The present study aims to scientifically document the uses of plant species for medicinal purposes, in the Sete Cidades. Twenty-eight community members from 40 to 84 years of age, of whom half were 55 to 64 years old, were interviewed. Twenty-nine taxa were reported as being used for medicinal purposes, ten of which have not been previously reported for ethnomedicinal use in Portugal, with a first record of the use of Morella faya. Leaves were the most used plant part (55%), and decoction the most common preparation mode. The five reported taxa with both the highest use value (0.71-0.25) and relative frequency of citation (0.14-0.11) were Clinopodium menthifolium subsp. ascendens, Aloysia citriodora, Mentha x piperita, Citrus limon and Rosmarinus officinalis. The traditional uses of some of the reported plants are supported by scientific studies, confirming their ethnomedicinal value and the need to preserve local knowledge of folk medicine practices.

12.
Rev. CEFAC ; 20(5): 680-687, Sept.-Oct. 2018. tab, graf
Artigo em Inglês | LILACS | ID: biblio-976880

RESUMO

ABSTRACT The purpose was to compare differences in production of plosive phonemes through the voice onset time (VOT) measurement in the speech of monolingual children, speakers of Brazilian Portuguese and bilingual children, speakers of both Brazilian Portuguese and English. The sample consisted of three monolingual children and three bilingual children; average age was 7 years. A speech emission was recorded for the investigation, which had the following vehicle phrase: "Diga 'papa' baixinho" ("Say 'papa' quietly"). Papa was then replaced by "baba", "tata", "dada", "caca" and "gaga". The measurements of the acoustic signals were performed through broadband spectrograms, and VOT was descriptively analyzed for the non-voiced sounds [p, t, k] and voiced [b, d, g] plosive sounds. Monolingual children presented higher average VOT values for [p, t, k] compared to bilingual children. For the [b, d, g] sounds, monolingual children had lower average VOT values, as compared to bilingual children. It was concluded that in the comparison of VOT measures of the speech samples, the monolingual children of Brazilian Portuguese presented higher values for the non voiced ones and lower for the voiced ones in relation to the bilingual children speakers of Brazilian Portuguese and English.


RESUMO O objetivo foi comparar as diferenças na produção de fonemas plosivos por meio da medida acústica voice onset time a partir da amostra de fala de três crianças monolíngues do português brasileiro e três bilíngues do português brasileiro e do inglês, na faixa etária de sete anos. Para isso foi gravada uma emissão de fala com a repetição da frase veículo "Diga papa baixinho", com a gravação posterior da substituição de papa por "baba, tata, dada, caca e gaga". As medidas do sinal acústico foram realizadas por meio do espectrograma de banda larga e o voice onset time (VOT) analisado de forma descritiva para os sons não vozeados [p, t, k] e para os vozeados [b, d, g]. Como resultados, os valores do VOT de [p, t, k] das crianças monolíngües apresentaram médias superiores em relação aos valores das crianças bilíngues. Para os sons [b, d, g] as crianças monolíngues mostraram valores de VOT com médias inferiores em relação às bilíngues. Concluiu-se que na comparação das medidas de VOT das amostras de fala as crianças monolíngues do português brasileiro apresentaram valores maiores para as não vozeadas e menores para as vozeadas em relação as das crianças bilíngues do português brasileiro e do inglês.

13.
Int J Surg Case Rep ; 51: 174-177, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30173077

RESUMO

INTRODUCTION: Posterior retroperitoneoscopic adrenalectomy has advantages over transperitoneal technique. However many surgeons prefer the transperitoneal technique because they get a familiar and wider working space. MATERIAL AND METHODS: A retrospective analysis of the first 10 patients submitted to posterior retroperitoneoscopic adrenalectomy was conducted. Data collected included: diagnosis, size, operation time, blood loss, conversion rate, morbidity and mortality, in-hospital length of stay. Compare our outcomes with worldwide bigger series, and take conclusions on the feasibility of the technique was the objective. RESULTS: We included 2 pheochromocytomas, 1 giant cystic pheochromocytoma, 4 Conn's, 2 Cushing's, 1 non-functioning tumor with 4 cm. Mean operation time was 46,7 min for lesions ranging from 1,8 to 14 cm. Blood loss was negligible. One patient (10%) was converted to laparotomy because of a past clinical history of dorsal and lumbar trauma. No morbidity and no mortality. Mean hospital length of stay was 2,2 days. DISCUSSION: Mean operation time found in bigger series published in worldwide literature is 40-105,6 min. Complication rate reported ranges from 0 to 14,4%. No mortality has been ever reported. Blood loss reported in other series is 10-50 ml. The data found in our study matches other studies data. Since the same surgeon who had never performed the technique before operated all patients, makes us believe the technique is safe and feasible. CONCLUSION: Posterior retroperitoneoscopic adrenalectomy has a small learning curve. It is technically safe and feasible. More patients will be collected to validate these results.

14.
Biochim Biophys Acta Bioenerg ; 1858(9): 733-741, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28377068

RESUMO

Gene knock-out studies on Geobacter sulfurreducens cells showed that the outer membrane-associated monoheme cytochrome OmcF is involved in respiratory pathways leading to the extracellular reduction of Fe(III) and U(VI). In addition, microarray analysis of an OmcF-deficient mutant revealed that many of the genes with decreased transcript level were those whose expression is up-regulated in cells grown with a graphite electrode as electron acceptor, suggesting that OmcF also regulates the electron transfer to electrode surfaces and the concomitant electricity production by G. sulfurreducens in microbial fuel cells. 15N,13C-labeled OmcF was produced and NMR spectroscopy was used to determine the solution structure of the protein in the fully reduced state and the pH-dependent conformational changes. In addition, 15N relaxation NMR experiments were used to characterize the overall and internal backbone dynamics of OmcF. The structure obtained is well-defined, with an average pairwise root mean square deviation of 0.37Å for the backbone atoms and 0.98Å for all heavy atoms. For the first time a solution structure and the protein motions were determined for an outer membrane cytochrome from G. sulfurreducens, which constitutes an important step to understand the extracellular electron transfer mechanism in Geobacter cells.


Assuntos
Proteínas de Bactérias/química , Geobacter/química , Heme/química , Modelos Moleculares , Movimento (Física) , Ressonância Magnética Nuclear Biomolecular , Oxirredução , Fragmentos de Peptídeos/química , Conformação Proteica , Proteínas Recombinantes/química , Soluções
15.
J Phys Chem B ; 120(39): 10221-10233, 2016 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-27603556

RESUMO

A family of triheme cytochromes from Geobacter sulfurreducens plays an important role in extracellular electron transfer. In addition to their role in electron transfer pathways, two members of this family (PpcA and PpcD) were also found to be able to couple e-/H+ transfer through the redox Bohr effect observed in the physiological pH range, a feature not observed for cytochromes PpcB and PpcE. In attempting to understand the molecular control of the redox Bohr effect in this family of cytochromes, which is highly homologous both in amino acid sequence and structures, it was observed that residue 6 is a conserved leucine in PpcA and PpcD, whereas in the other two characterized members (PpcB and PpcE) the equivalent residue is a phenylalanine. To determine the role of this residue located close to the redox Bohr center, we replaced Leu6 in PpcA with Phe and determined the redox properties of the mutant, as well as its solution structure in the fully reduced state. In contrast with the native form, the mutant PpcAL6F is not able to couple the e-/H+ pathway. We carried out the reverse mutation in PpcB and PpcE (i.e., replacing Phe6 in these two proteins by leucine) and the mutated proteins showed an increased redox Bohr effect. The results clearly establish the role of residue 6 in the control of the redox Bohr effect in this family of cytochromes, a feature that could enable the rational design of G. sulfurreducens strains that carry mutant cytochromes with an optimal redox Bohr effect that would be suitable for various biotechnological applications.


Assuntos
Citocromos/metabolismo , Geobacter/química , Termodinâmica , Citocromos/química , Citocromos/genética , Transporte de Elétrons , Geobacter/crescimento & desenvolvimento , Geobacter/metabolismo , Concentração de Íons de Hidrogênio , Modelos Moleculares , Mutagênese Sítio-Dirigida , Oxirredução , Conformação Proteica
16.
Dalton Trans ; 44(20): 9335-44, 2015 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-25906375

RESUMO

Geobacter bacteria have a remarkable respiratory versatility that includes the dissimilatory reduction of insoluble metal oxides in natural habitats and electron transfer to electrode surfaces from which electricity can be harvested. In both cases, electrons need to be exported from the cell interior to the exterior via a mechanism designated as extracellular electron transfer (EET). Several c-type cytochromes from G. sulfurreducens (Gs) were identified as key players in this process. Biochemical and biophysical data have been obtained for ten Gs cytochromes, including inner-membrane associated (MacA), periplasmic (PpcA, PpcB, PpcC, PpcD, PpcE and GSU1996) and outer membrane-associated (OmcF, OmcS and OmcZ). The redox properties of these cytochromes have been determined, except for PpcC and GSU1996. In this perspective, the reduction potentials of these two cytochromes were determined by potentiometric redox titrations followed by visible spectroscopy. The data obtained are taken together with those available for other key cytochromes to present a thorough overview of the current knowledge of Gs EET mechanisms and provide a possible rationalization for the existence of several multiheme cytochromes involved in the same respiratory pathways.


Assuntos
Citocromos/metabolismo , Espaço Extracelular/metabolismo , Geobacter/citologia , Geobacter/enzimologia , Transporte de Elétrons , Geobacter/metabolismo
17.
Biochim Biophys Acta ; 1837(6): 920-8, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24463054

RESUMO

The periplasmic sensor domains GSU582 and GSU935 are part of methyl-accepting chemotaxis proteins of the bacterium Geobacter sulfurreducens containing one c-type heme and a PAS-like fold. Their spectroscopic properties were shown previously to share similar spectral features. In both sensors, the heme group is in the high-spin form in the oxidized state and low-spin after reduction and binding of a methionine residue. Therefore, it was proposed that this redox-linked ligand switch might be related to the signal transduction mechanism. We now report the thermodynamic and kinetic characterization of the sensors GSU582 and GSU935 by visible spectroscopy and stopped-flow techniques, at several pH and ionic strength values. Despite their similar spectroscopic features, the midpoint reduction potentials and the rate constants for reduction by dithionite are considerably different in the two sensors. The reduction potentials of both sensors are negative and well framed within the typical anoxic subsurface environments in which Geobacter species predominate. The midpoint reduction potentials of sensor GSU935 are lower than those of GSU582 at all pH and ionic strength values and the same was observed for the reduction rate constants. The origin of the different functional properties of these closely related sensors is rationalized in the terms of the structures. The results suggest that the sensors are designed to function in different working potential ranges, allowing the bacteria to trigger an adequate cellular response in different anoxic subsurface environments. These findings provide an explanation for the co-existence of two similar methyl-accepting chemotaxis proteins in G. sulfurreducens.


Assuntos
Proteínas de Bactérias/química , Quimiotaxia , Geobacter/química , Heme/química , Termodinâmica , Concentração de Íons de Hidrogênio , Cinética , Concentração Osmolar , Conformação Proteica , Espectrofotometria Ultravioleta
18.
Distúrb. comun ; 25(2)ago 2013.
Artigo em Português | LILACS | ID: lil-686936

RESUMO

O objetivo desta comunicação foi apresentar de forma reflexiva a experiência da atuação fonoaudiológica junto à formação profissional em rádio e televisãoI. A partir da experiência ocorrida na disciplina de Fonoplastia de um Curso Superior de Tecnologia em Produção Audiovisual, evidenciamos a real contribuição da Fonoaudiologia no trabalho com a comunicação, não verbal e verbal, assim como todos os aspectos relacionados à expressividade do discurso dos alunos. O progresso foi evidente e sentido de forma ampla em outras disciplinas como, por exemplo, Locução de Rádio e Apresentação para Televisão.Desta forma, temos clareza do papel fundamental que as disciplinas relacionadas à Fonoaudiologia exercem para esse tipo de formação. Mesmo assim, sabe-se que nos cursos profissionalizantes e acadêmicos essa inserção do fonoaudiólogo não é consensual. Por essa razão, apontamos de forma descritiva, nesta comunicação, a sua importância e necessidade...


The purpose of this communication was to present in a reflective way the experience of speech therapy with professional training on radio and television. From the experience occurred in the subject of speech design, it has been highlighted the real contribution of speech therapy in working with non-verbal and verbal communication, as well as all aspects of the expressiveness of the speech of students. Progress has been evident in a broad sense and in other subjects such as, for instance, the radio voiceover and the presentation for television. Thus, it has become evident for us the essential role of those subjects related to speech therapy for this type of exercise training. Even so, it is known that for the academic and vocational courses, the insertion of a speech therapist is not consensual. For this reason, it is pointed out descriptively, on this communication, its importance and necessity...


El objetivo de esta comunicación fue la de presentar de manera reflexiva la experiencia de la actuación fonoaudiológica junto a la formación profesional en radio y televisión. Desde la experiencia que se ha pasado en la asignatura de Fonoplastia en un Curso Superior de Tecnologia en Producción Audiovisual, evidenciamos la real contribución de la Fonoaudiologia en el trabajo de la comunicación verbal y no verbal, así como todos los aspectos relacionados a la expresividad del discurso de los alumnos. El progreso fue evidente y sentido de manera amplia en las otras asignaturas, como, por ejemplo, Locución de Radio y Presentación para Tele. Así, tenemos claro el papel fundamental que las asignaturas relativas a la Fonoaudiologia ejercen a este tipo de formación. Au asi, se sabe que en los cursos de formación profesional y académica la insersión del fonoaudiólogo no es concensual. Por esta razón, apuntamos de manera descritiva, en esta comunicación, su importancia y necesidad...


Assuntos
Humanos , Rádio , Fonoaudiologia , Televisão , Voz
19.
Distúrb. comun ; 25(2): 293-296, ago 2013.
Artigo em Português | Index Psicologia - Periódicos | ID: psi-62045

RESUMO

O objetivo desta comunicação foi apresentar de forma reflexiva a experiência da atuação fonoaudiológica junto à formação profissional em rádio e televisãoI. A partir da experiência ocorrida na disciplina de Fonoplastia de um Curso Superior de Tecnologia em Produção Audiovisual, evidenciamos a real contribuição da Fonoaudiologia no trabalho com a comunicação, não verbal e verbal, assim como todos os aspectos relacionados à expressividade do discurso dos alunos. O progresso foi evidente e sentido de forma ampla em outras disciplinas como, por exemplo, Locução de Rádio e Apresentação para Televisão.Desta forma, temos clareza do papel fundamental que as disciplinas relacionadas à Fonoaudiologia exercem para esse tipo de formação. Mesmo assim, sabe-se que nos cursos profissionalizantes e acadêmicos essa inserção do fonoaudiólogo não é consensual. Por essa razão, apontamos de forma descritiva, nesta comunicação, a sua importância e necessidade.(AU)(AU)


The purpose of this communication was to present in a reflective way the experience of speech therapy with professional training on radio and television. From the experience occurred in the subject of speech design, it has been highlighted the real contribution of speech therapy in working with non-verbal and verbal communication, as well as all aspects of the expressiveness of the speech of students. Progress has been evident in a broad sense and in other subjects such as, for instance, the radio voiceover and the presentation for television. Thus, it has become evident for us the essential role of those subjects related to speech therapy for this type of exercise training. Even so, it is known that for the academic and vocational courses, the insertion of a speech therapist is not consensual. For this reason, it is pointed out descriptively, on this communication, its importance and necessity.(AU)(AU)


El objetivo de esta comunicación fue la de presentar de manera reflexiva la experiencia de la actuación fonoaudiológica junto a la formación profesional en radio y televisión. Desde la experiencia que se ha pasado en la asignatura de Fonoplastia en un Curso Superior de Tecnologia en Producción Audiovisual, evidenciamos la real contribución de la Fonoaudiologia en el trabajo de la comunicación verbal y no verbal, así como todos los aspectos relacionados a la expresividad del discurso de los alumnos. El progreso fue evidente y sentido de manera amplia en las otras asignaturas, como, por ejemplo, Locución de Radio y Presentación para Tele. Así, tenemos claro el papel fundamental que las asignaturas relativas a la Fonoaudiologia ejercen a este tipo de formación. Au asi, se sabe que en los cursos de formación profesional y académica la insersión del fonoaudiólogo no es concensual. Por esta razón, apuntamos de manera descritiva, en esta comunicación, su importancia y necesidad.(AU)(AU)


Assuntos
Humanos , Televisão , Rádio , Voz , Fonoaudiologia
20.
Biochem Soc Trans ; 40(6): 1295-301, 2012 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-23176471

RESUMO

Extracellular electron transfer is one of the physiological hallmarks of Geobacter sulfurreducens, allowing these bacteria to reduce toxic and/or radioactive metals and grow on electrode surfaces. Aiming to functionally optimize the respiratory electron-transfer chains, such properties can be explored through genetically engineered strains. Geobacter species comprise a large number of different multihaem c-type cytochromes involved in the extracellular electron-transfer pathways. The functional characterization of multihaem proteins is particularly complex because of the coexistence of several microstates in solution, connecting the fully reduced and oxidized states. NMR spectroscopy has been used to monitor the stepwise oxidation of each individual haem and thus to obtain information on each microstate. For the structural study of these proteins, a cost-effective isotopic labelling of the protein polypeptide chains was combined with the comparative analysis of 1H-13C HSQC (heteronuclear single-quantum correlation) NMR spectra obtained for labelled and unlabelled samples. These new methodological approaches allowed us to study G. sulfurreducens haem proteins functionally and structurally, revealing functional mechanisms and key residues involved in their electron-transfer capabilities. Such advances can now be applied to the design of engineered haem proteins to improve the bioremediation and electricity-harvesting skills of G. sulfurreducens.


Assuntos
Proteínas de Bactérias/metabolismo , Citocromos/metabolismo , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Biodegradação Ambiental , Biotecnologia , Citocromos/química , Citocromos/genética , Transporte de Elétrons , Compostos Férricos/metabolismo , Geobacter/genética , Modelos Biológicos , Oxirredução , Conformação Proteica
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