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1.
Data Brief ; 52: 109915, 2024 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-38229924

RESUMEN

Space-occupying lesions (SOL) brain detected on brain MRI are benign and malignant tumors. Several brain tumor segmentation algorithms have been developed but there is a need for a clinically acquired dataset that is used for real-time images. This research is done to facilitate reporting of MRI done for brain tumor detection by incorporating computer-aided detection. Another objective was to make reporting unbiased by decreasing inter-observer errors and expediting daily reporting sessions to decrease radiologists' workload. This is an experimental study. The proposed dataset contains clinically acquired multiplanar, multi-sequential MRI slices (MPMSI) which are used as input to the segmentation model without any preprocessing. The proposed AJBDS-2023 consists of 10667 images of real patients imaging data with a size of 320*320*3. Acquired images have T1W, TW2, Flair, T1W contrast, ADC, and DWI sequences. Pixel-based ground-truth annotated images of the tumor core and edema of 6334 slices are made manually under the supervision of a radiologist. Quantitative assessment of AJBDS-2023 images is done by a novel U-network on 4333 MRI slices. The diagnostic accuracy of our algorithm U-Net trained on AJBDS-2023 was 77.4 precision, 82.3 DSC, 87.4 specificity, 93.8 sensitivity, and 90.4 confidence interval. An experimental analysis of AJBDS-2023 done by the U-Net segmentation model proves that the proposed AJBDS-2023 dataset has images without preprocessing, which is more challenging and provides a more realistic platform for evaluation and analysis of newly developed algorithms in this domain and helps radiologists in MRI brain reporting more realistically.

2.
BMC Plant Biol ; 23(1): 437, 2023 Sep 19.
Artículo en Inglés | MEDLINE | ID: mdl-37723493

RESUMEN

BACKGROUND: To decipher the capability of Methyl Jasmonate (MeJA) in resisting cold stress in Solanum lycopersicum assessment regarding various physiological parameters in response to diverse doses of MeJA was done. Low temperature (LT) were given to the plants with MeJA (J1C, J2C, J3C) or without MeJA (LT) application. MeJA in the form of foliar spray was given before stress, during stress and after stress. Three concentrations of MeJA were used under normal and LT stress conditions that includes of J1 (0.5 µM), J2 (10 µM), and J3 (15 µM). RESULTS: Oxidative stress, growth characteristics, stress tolerance parameters, antioxidant response and photosynthetic parameters were investigated. In our current study we observed that oxidative stress markers declined by MeJA supplementation under cold stress conditions. MeJA boosted antioxidant enzyme activity along with photosynthetic parameters. The best concentration of MeJA was J2 based on results obtained. This is the first study related to MeJA best dose screening in Solanum lycopersicum under LT stress conditions. CONCLUSION: The LT stress in the Solanum lycopersicum plant was reduced by MeJA. The adverse consequences of LT stress can be significantly attenuated by the J2 concentration of MeJA. So, the optimal concentration of MeJA supplied exogenously to LT stressed Solanum lycopersicum can be a smart strategy to mitigate harmful impact of LT stress on detox system and overall growth of plant.


Asunto(s)
Antioxidantes , Solanum lycopersicum , Temperatura , Acetatos/farmacología
3.
Nat Commun ; 14(1): 3479, 2023 06 13.
Artículo en Inglés | MEDLINE | ID: mdl-37311819

RESUMEN

Selenium homeostasis depends on hepatic biosynthesis of selenoprotein P (SELENOP) and SELENOP-mediated transport from the liver to e.g. the brain. In addition, the liver maintains copper homeostasis. Selenium and copper metabolism are inversely regulated, as increasing copper and decreasing selenium levels are observed in blood during aging and inflammation. Here we show that copper treatment increased intracellular selenium and SELENOP in hepatocytes and decreased extracellular SELENOP levels. Hepatic accumulation of copper is a characteristic of Wilson's disease. Accordingly, SELENOP levels were low in serum of Wilson's disease patients and Wilson's rats. Mechanistically, drugs targeting protein transport in the Golgi complex mimicked some of the effects observed, indicating a disrupting effect of excessive copper on intracellular SELENOP transport resulting in its accumulation in the late Golgi. Our data suggest that hepatic copper levels determine SELENOP release from the liver and may affect selenium transport to peripheral organs such as the brain.


Asunto(s)
Degeneración Hepatolenticular , Selenio , Animales , Ratas , Selenoproteína P , Cobre
4.
Diagnostics (Basel) ; 13(9)2023 Apr 29.
Artículo en Inglés | MEDLINE | ID: mdl-37174985

RESUMEN

Lung and colon cancers are among the leading causes of human mortality and morbidity. Early diagnostic work up of these diseases include radiography, ultrasound, magnetic resonance imaging, and computed tomography. Certain blood tumor markers for carcinoma lung and colon also aid in the diagnosis. Despite the lab and diagnostic imaging, histopathology remains the gold standard, which provides cell-level images of tissue under examination. To read these images, a histopathologist spends a large amount of time. Furthermore, using conventional diagnostic methods involve high-end equipment as well. This leads to limited number of patients getting final diagnosis and early treatment. In addition, there are chances of inter-observer errors. In recent years, deep learning has shown promising results in the medical field. This has helped in early diagnosis and treatment according to severity of disease. With the help of EffcientNetV2 models that have been cross-validated and tested fivefold, we propose an automated method for detecting lung (lung adenocarcinoma, lung benign, and lung squamous cell carcinoma) and colon (colon adenocarcinoma and colon benign) cancer subtypes from LC25000 histopathology images. A state-of-the-art deep learning architecture based on the principles of compound scaling and progressive learning, EffcientNetV2 large, medium, and small models. An accuracy of 99.97%, AUC of 99.99%, F1-score of 99.97%, balanced accuracy of 99.97%, and Matthew's correlation coefficient of 99.96% were obtained on the test set using the EffcientNetV2-L model for the 5-class classification of lung and colon cancers, outperforming the existing methods. Using gradCAM, we created visual saliency maps to precisely locate the vital regions in the histopathology images from the test set where the models put more attention during cancer subtype predictions. This visual saliency maps may potentially assist pathologists to design better treatment strategies. Therefore, it is possible to use the proposed pipeline in clinical settings for fully automated lung and colon cancer detection from histopathology images with explainability.

5.
Fitoterapia ; 162: 105268, 2022 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-35963483

RESUMEN

The main objective of our present research work was to explore molecular insight for potentially active new acetylcholinesterase inhibitor from the aerial parts of Delphinium uncinatum. New norditerpenoid alkaloids, uncinatine-A, was isolated from the basic alkaloidal fraction of D. uncinatum, based on bioactivity guided isolation. The structure of uncinatine-A was determined through latest spectroscopic techniques including single X-Ray diffraction technique. The structural data and electronic properties of uncinatine-A was also calculated by Density Functional Theory (DFT) using B3LYP/6-31þ G (p) basis set. The isolated natural product was evaluated for their acetyl cholinesterase inhibitory potential in dose dependent protocol (62.5-1000 µg/mL), followed by molecular docking studies. Significant competitive type inhibition activity (IC50 = 207.73 ± 0.3) was shown by isolated natural norditerpenoid against cholinesterase targets in comparison with standard drugs available in the market such as galanthamine. The molecular docking results showed that isolated natural product was well accommodated by AChE in the active site with docking scores -11.0326. This is the first report indicating uncinatine-A as a potent acetylcholinesterase inhibitor and can be used as a target drug in cerebral dementia and Alzheimer diseases.


Asunto(s)
Alcaloides , Productos Biológicos , Delphinium , Diterpenos , Acetilcolinesterasa/metabolismo , Inhibidores de la Colinesterasa , Delphinium/química , Teoría Funcional de la Densidad , Galantamina , Simulación del Acoplamiento Molecular , Estructura Molecular
6.
Sci Rep ; 12(1): 12548, 2022 07 22.
Artículo en Inglés | MEDLINE | ID: mdl-35869119

RESUMEN

To investigate the impact of Glutathione (GSH) in mitigating low-temperature stress in Pusa Sheetal cv. of Solanum lycopersicum and imparting low-temperature tolerance by evaluating the different physiological responses. The plant under research was also being studied for its growth and stress tolerance. Low temperatures (LT) stress was applied to seedlings with or without GSH application 12 h before LT stress (prophylactic dose), after 12 h-LT (preemptive dose), and post 12-h recovery (curative dose). Different concentrations of GSH [0, G1 (0.5 mM), G2 (1 mM) and G3 (2 mM)] against LT stress were used. Antioxidant activities, photosynthesis, growth, and stress tolerance indices were quantified. LT stress caused an oxidative burst in S. lycopersicum seedlings of the Pusa Sheetal cv. as indicated by increased peroxidation of lipids and H2O2 concentration. Glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities were enhanced. The best concentration was G2 (1 mM), which resulted in a rise in antioxidant activity. Moreover, a decline in lipid peroxidation and H2O2 levels was also seen. The purpose of this study is to identify the role of GSH in reducing LT stress and to find the best dose concentration. This is the first report to assess the GSH-mediated LT stress tolerance in S. lycopersicum (Pusa Sheetal cv.). Therefore, exogenous GSH application of optimal concentration of GSH to LT stressed S. lycopersicum can be an effective approach for augmenting the plant detoxification system and promoting its growth and development.


Asunto(s)
Solanum lycopersicum , Antioxidantes/metabolismo , Catalasa/metabolismo , Glutatión/metabolismo , Peróxido de Hidrógeno/farmacología , Solanum lycopersicum/metabolismo , Estrés Oxidativo , Plantones/metabolismo , Superóxido Dismutasa/metabolismo , Temperatura
7.
Cognit Comput ; 14(5): 1677-1688, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-34394762

RESUMEN

Background: COVID-19 is a novel virus that affects the upper respiratory tract, as well as the lungs. The scale of the global COVID-19 pandemic, its spreading rate, and deaths are increasing regularly. Computed tomography (CT) scans can be used carefully to detect and analyze COVID-19 cases. In CT images/scans, ground-glass opacity (GGO) is found in the early stages of infection. While in later stages, there is a superimposed pulmonary consolidation. Methods: This research investigates the quantum machine learning (QML) and classical machine learning (CML) approaches for the analysis of COVID-19 images. The recent developments in quantum computing have led researchers to explore new ideas and approaches using QML. The proposed approach consists of two phases: in phase I, synthetic CT images are generated through the conditional adversarial network (CGAN) to increase the size of the dataset for accurate training and testing. In phase II, the classification of COVID-19/healthy images is performed, in which two models are proposed: CML and QML. Result: The proposed model achieved 0.94 precision (Pn), 0.94 accuracy (Ac), 0.94 recall (Rl), and 0.94 F1-score (Fe) on POF Hospital dataset while 0.96 Pn, 0.96 Ac, 0.95 Rl, and 0.96 Fe on UCSD-AI4H dataset. Conclusion: The proposed method achieved better results when compared to the latest published work in this domain.

8.
Front Plant Sci ; 12: 668029, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34367199

RESUMEN

Plant growth regulators have an important role in various developmental processes during the life cycle of plants. They are involved in abiotic stress responses and tolerance. They have very well-developed capabilities to sense the changes in their external milieu and initiate an appropriate signaling cascade that leads to the activation of plant defense mechanisms. The plant defense system activation causes build-up of plant defense hormones like jasmonic acid (JA) and antioxidant systems like glutathione (GSH). Moreover, calcium (Ca2+) transients are also seen during abiotic stress conditions depicting the role of Ca2+ in alleviating abiotic stress as well. Therefore, these growth regulators tend to control plant growth under varying abiotic stresses by regulating its oxidative defense and detoxification system. This review highlights the role of Jasmonates, Calcium, and glutathione in abiotic stress tolerance and activation of possible novel interlinked signaling cascade between them. Further, phyto-hormone crosstalk with jasmonates, calcium and glutathione under abiotic stress conditions followed by brief insights on omics approaches is also elucidated.

9.
Antioxidants (Basel) ; 10(2)2021 Feb 04.
Artículo en Inglés | MEDLINE | ID: mdl-33557356

RESUMEN

Dietary antioxidants and supplements are widely used to protect against cancer, even though it is now clear that antioxidants can promote tumor progression by helping cancer cells to overcome barriers of oxidative stress. Although recent studies have, in great detail, explored the role of antioxidants in lung and skin tumors driven by RAS and RAF mutations, little is known about the impact of antioxidant supplementation on other cancers, including Wnt-driven tumors originating from the gut. Here, we show that supplementation with the antioxidants N-acetylcysteine (NAC) and vitamin E promotes intestinal tumor progression in the ApcMin mouse model for familial adenomatous polyposis, a hereditary form of colorectal cancer, driven by Wnt signaling. Both antioxidants increased tumor size in early neoplasias and tumor grades in more advanced lesions without any impact on tumor initiation. Importantly, NAC treatment accelerated tumor progression at plasma concentrations comparable to those obtained in human subjects after prescription doses of the drug. These results demonstrate that antioxidants play an important role in the progression of intestinal tumors, which may have implications for patients with or predisposed to colorectal cancer.

10.
Sci Rep ; 10(1): 14156, 2020 08 25.
Artículo en Inglés | MEDLINE | ID: mdl-32843651

RESUMEN

Recent data suggest that the transcription factor Zfp148 represses activation of the tumor suppressor p53 in mice and that therapeutic targeting of the human orthologue ZNF148 could activate the p53 pathway without causing detrimental side effects. We have previously shown that Zfp148 deficiency promotes p53-dependent proliferation arrest of mouse embryonic fibroblasts (MEFs), but the underlying mechanism is not clear. Here, we showed that Zfp148 deficiency downregulated cell cycle genes in MEFs in a p53-dependent manner. Proliferation arrest of Zfp148-deficient cells required increased expression of ARF, a potent activator of the p53 pathway. Chromatin immunoprecipitation showed that Zfp148 bound to the ARF promoter, suggesting that Zfp148 represses ARF transcription. However, Zfp148 preferentially bound to promoters of other transcription factors, indicating that deletion of Zfp148 may have pleiotropic effects that activate ARF and p53 indirectly. In line with this, we found no evidence of genetic interaction between TP53 and ZNF148 in CRISPR and siRNA screen data from hundreds of human cancer cell lines. We conclude that Zfp148 deficiency, by increasing ARF transcription, downregulates cell cycle genes and cell proliferation in a p53-dependent manner. However, the lack of genetic interaction between ZNF148 and TP53 in human cancer cells suggests that therapeutic targeting of ZNF148 may not increase p53 activity in humans.


Asunto(s)
Proteínas de Unión al ADN/genética , Regulación de la Expresión Génica/genética , Transducción de Señal/genética , Factores de Transcripción/genética , Proteína p53 Supresora de Tumor/fisiología , Animales , Sistemas CRISPR-Cas , Puntos de Control del Ciclo Celular/genética , Proteínas de Ciclo Celular/biosíntesis , Proteínas de Ciclo Celular/genética , División Celular , Línea Celular , Inmunoprecipitación de Cromatina , Cisplatino/toxicidad , Inhibidor p16 de la Quinasa Dependiente de Ciclina/metabolismo , Daño del ADN , Proteínas de Unión al ADN/deficiencia , Proteínas de Unión al ADN/fisiología , Regulación hacia Abajo , Factores de Transcripción E2F/fisiología , Etopósido/toxicidad , Fibroblastos , Ontología de Genes , Ratones , Interferencia de ARN , ARN Interferente Pequeño/genética , Factores de Transcripción/deficiencia , Factores de Transcripción/fisiología
11.
J Med Syst ; 44(2): 32, 2019 Dec 17.
Artículo en Inglés | MEDLINE | ID: mdl-31848728

RESUMEN

Brain tumor detection depicts a tough job because of its shape, size and appearance variations. In this manuscript, a deep learning model is deployed to predict input slices as a tumor (unhealthy)/non-tumor (healthy). This manuscript employs a high pass filter image to prominent the inhomogeneities field effect of the MR slices and fused with the input slices. Moreover, the median filter is applied to the fused slices. The resultant slices quality is improved with smoothen and highlighted edges of the input slices. After that, based on these slices' intensity, a 4-connected seed growing algorithm is applied, where optimal threshold clusters the similar pixels from the input slices. The segmented slices are then supplied to the fine-tuned two layers proposed stacked sparse autoencoder (SSAE) model. The hyperparameters of the model are selected after extensive experiments. At the first layer, 200 hidden units and at the second layer 400 hidden units are utilized. The testing is performed on the softmax layer for the prediction of the images having tumors and no tumors. The suggested model is trained and checked on BRATS datasets i.e., 2012(challenge and synthetic), 2013, and 2013 Leaderboard, 2014, and 2015 datasets. The presented model is evaluated with a number of performance metrics which demonstrates the improved performance.


Asunto(s)
Algoritmos , Neoplasias Encefálicas/diagnóstico por imagen , Neoplasias Encefálicas/patología , Aprendizaje Profundo , Diagnóstico por Computador/métodos , Humanos , Procesamiento de Imagen Asistido por Computador/métodos
12.
Sci Rep ; 9(1): 14667, 2019 10 11.
Artículo en Inglés | MEDLINE | ID: mdl-31604991

RESUMEN

The mut-T homolog-1 (MTH1) inhibitor TH588 has shown promise in preclinical cancer studies but its targeting specificity has been questioned. Alternative mechanisms for the anti-cancer effects of TH588 have been suggested but the question remains unresolved. Here, we performed an unbiased CRISPR screen on human lung cancer cells to identify potential mechanisms behind the cytotoxic effect of TH588. The screen identified pathways and complexes involved in mitotic spindle regulation. Using immunofluorescence and live cell imaging, we showed that TH588 rapidly reduced microtubule plus-end mobility, disrupted mitotic spindles, and prolonged mitosis in a concentration-dependent but MTH1-independent manner. These effects activated a USP28-p53 pathway - the mitotic surveillance pathway - that blocked cell cycle reentry after prolonged mitosis; USP28 acted upstream of p53 to arrest TH588-treated cells in the G1-phase of the cell cycle. We conclude that TH588 is a microtubule-modulating agent that activates the mitotic surveillance pathway and thus prevents cancer cells from re-entering the cell cycle.


Asunto(s)
Carcinoma de Células Grandes/tratamiento farmacológico , Enzimas Reparadoras del ADN/genética , Monoéster Fosfórico Hidrolasas/genética , Pirimidinas/farmacología , Ubiquitina Tiolesterasa/genética , Antineoplásicos/farmacología , Sistemas CRISPR-Cas/genética , Carcinoma de Células Grandes/genética , Carcinoma de Células Grandes/patología , Ciclo Celular/efectos de los fármacos , Línea Celular Tumoral , Enzimas Reparadoras del ADN/antagonistas & inhibidores , Fase G1/efectos de los fármacos , Regulación Neoplásica de la Expresión Génica/efectos de los fármacos , Humanos , Microtúbulos/efectos de los fármacos , Mitosis/efectos de los fármacos , Monoéster Fosfórico Hidrolasas/antagonistas & inhibidores , Huso Acromático/efectos de los fármacos , Moduladores de Tubulina/farmacología , Proteína p53 Supresora de Tumor/genética
13.
Oncotarget ; 7(35): 56183-56192, 2016 Aug 30.
Artículo en Inglés | MEDLINE | ID: mdl-27487143

RESUMEN

The transcription factor Zinc finger protein 148 (Zfp148, ZBP-89, BFCOL, BERF1, htß) interacts physically with the tumor suppressor p53, but the significance of this interaction is not known. We recently showed that knockout of Zfp148 in mice leads to ectopic activation of p53 in some tissues and cultured fibroblasts, suggesting that Zfp148 represses p53 activity. Here we hypothesize that targeting Zfp148 would unleash p53 activity and protect against cancer development, and test this idea in the APCMin/+ mouse model of intestinal adenomas. Loss of one copy of Zfp148 markedly reduced tumor numbers and tumor-associated intestinal bleedings, and improved survival. Furthermore, after activation of ß-catenin-the initiating event in colorectal cancer-Zfp148 deficiency activated p53 and induced apoptosis in intestinal explants of APCMin/+ mice. The anti-tumor effect of targeting Zfp148 depended on p53, as Zfp148 deficiency did not affect tumor numbers in APCMin/+ mice lacking one or both copies of Trp53. The results suggest that Zfp148 controls the fate of newly transformed intestinal tumor cells by repressing p53 and that targeting Zfp148 might be useful in the treatment of colorectal cancer.


Asunto(s)
Adenoma/patología , Neoplasias Colorrectales/patología , Proteínas de Unión al ADN/metabolismo , Hemorragia Gastrointestinal/patología , Factores de Transcripción/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , Adenoma/mortalidad , Animales , Apoptosis , Proliferación Celular , Transformación Celular Neoplásica/patología , Células Cultivadas , Neoplasias Colorrectales/mortalidad , Proteínas de Unión al ADN/genética , Fibroblastos , Hemorragia Gastrointestinal/mortalidad , Humanos , Ratones , Ratones Noqueados , Neoplasias Experimentales/mortalidad , Neoplasias Experimentales/patología , Factores de Transcripción/genética , Proteína p53 Supresora de Tumor/genética , beta Catenina/metabolismo
14.
J Mol Biol ; 426(1): 136-49, 2014 Jan 09.
Artículo en Inglés | MEDLINE | ID: mdl-24041572

RESUMEN

The major barrier to the physical characterization and structure determination of membrane proteins is low protein yield and/or low functionality in recombinant expression. The enteric bacterium Escherichia coli is the most widely employed organism for producing recombinant proteins. Beside several advantages of this expression host, one major drawback is that the protein of interest does not always adopt its native conformation and may end up in large insoluble aggregates. We describe a robust strategy to increase the likelihood of overexpressing membrane proteins in a functional state. The method involves fusion in tandem of green fluorescent protein and the erythromycin resistance protein (23S ribosomal RNA adenine N-6 methyltransferase, ErmC) to the C-terminus of a target membrane protein. The fluorescence of green fluorescent protein is used to report the folding state of the target protein, whereas ErmC is used to select for increased expression. By gradually increasing the erythromycin concentration of the medium and testing different membrane protein targets, we obtained a number of evolved strains of which four (NG2, NG3, NG5 and NG6) were characterized and their genome was fully sequenced. Strikingly, each of the strains carried a mutation in the hns gene, whose product is involved in genome organization and transcriptional silencing. The degree of expression of (membrane) proteins correlates with the severity of the hns mutation, but cells in which hns was deleted showed an intermediate expression performance. We propose that (partial) removal of the transcriptional silencing mechanism changes the levels of proteins essential for the functional overexpression of membrane proteins.


Asunto(s)
Proteínas de Escherichia coli/biosíntesis , Escherichia coli/metabolismo , Expresión Génica , Proteínas de la Membrana/biosíntesis , Análisis Mutacional de ADN , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Proteínas Fimbrias/genética , Fluorometría , Genoma Bacteriano , Proteínas Fluorescentes Verdes/biosíntesis , Proteínas Fluorescentes Verdes/genética , Proteínas de la Membrana/genética , Metiltransferasas/biosíntesis , Metiltransferasas/genética , Mutación , Proteínas Recombinantes de Fusión/biosíntesis , Proteínas Recombinantes de Fusión/genética , Selección Genética , Análisis de Secuencia de ADN
15.
Mol Membr Biol ; 30(2): 138-48, 2013 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-23249124

RESUMEN

The ATP-binding cassette (ABC) transporter ProU from Escherichia coli translocates a wide range of compatible solutes and contributes to the regulation of cell volume, which is particularly important when the osmolality of the environment fluctuates. We have purified the components of ProU, i.e., the substrate-binding protein ProX, the nucleotide-binding protein ProV and the transmembrane protein ProW, and reconstituted the full transporter complex in liposomes. We engineered a lipid anchor to ProX for surface tethering of this protein to ProVW-containing proteoliposomes. We show that glycine betaine binds to ProX with high-affinity and is transported via ProXVW in an ATP-dependent manner. The activity ProU is salt and anionic lipid-dependent and mimics the ionic strength-gating of transport of the homologous OpuA system.


Asunto(s)
Transportadoras de Casetes de Unión a ATP/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Proteínas de Transporte de Membrana/metabolismo , Proteínas de Unión Periplasmáticas/metabolismo , Transportadoras de Casetes de Unión a ATP/genética , Betaína/metabolismo , Transporte Biológico , Proteínas Portadoras , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Liposomas/metabolismo , Proteínas de Transporte de Membrana/genética , Proteínas de Unión Periplasmáticas/genética , Proteolípidos/genética , Proteolípidos/metabolismo , Equilibrio Hidroelectrolítico/fisiología
16.
Biochemistry ; 51(25): 5142-52, 2012 Jun 26.
Artículo en Inglés | MEDLINE | ID: mdl-22656643

RESUMEN

The ATP-binding-cassette transporter OpuA from Lactococcus lactis is composed of two ATPase subunits (OpuAA) and two subunits (OpuABC) with the transmembrane domain fused to an extracellular substrate-binding protein. Of the almost 1900 homologues of OpuA known to date, a subset has an amino-terminal amphipathic helix (plus extra transmembrane segment) fused to the core of the transmembrane domain of the OpuABC subunit. FRET measurements indicate that the amphipathic α-helix is located close to the membrane surface, where its hydrophobic face interacts with the transport protein rather than the membrane lipids. Next, we determined the functional role of this accessory region by engineering the amphipathic α-helix. We analyzed the consequence of the mutations in intact cells by monitoring growth and transport of glycine betaine under normal and osmotic stress conditions. More detailed studies were performed in hybrid membrane vesicles, proteoliposomes, and bilayer nanodisks. We show that the amphipathic α-helix of OpuA is necessary for high activity of OpuA but is not critical for the biogenesis of the protein or the ionic regulation of transport.


Asunto(s)
Transportadoras de Casetes de Unión a ATP/química , Transportadoras de Casetes de Unión a ATP/fisiología , Adenosina Trifosfatasas/química , Adenosina Trifosfatasas/fisiología , Proteínas Bacterianas/química , Proteínas Bacterianas/fisiología , Lactococcus lactis/enzimología , Ósmosis/fisiología , Transportadoras de Casetes de Unión a ATP/biosíntesis , Transportadoras de Casetes de Unión a ATP/metabolismo , Adenosina Trifosfatasas/biosíntesis , Adenosina Trifosfatasas/metabolismo , Secuencia de Aminoácidos , Proteínas Bacterianas/biosíntesis , Proteínas Bacterianas/metabolismo , Activación del Canal Iónico/fisiología , Metabolismo de los Lípidos/fisiología , Datos de Secuencia Molecular , Estructura Secundaria de Proteína/fisiología , Subunidades de Proteína/química , Subunidades de Proteína/metabolismo , Subunidades de Proteína/fisiología , Transporte de Proteínas/fisiología , Proteolípidos/química , Proteolípidos/metabolismo , Proteolípidos/fisiología
17.
PLoS One ; 5(4): e10361, 2010 Apr 29.
Artículo en Inglés | MEDLINE | ID: mdl-20454456

RESUMEN

BACKGROUND: The ABC transporter OpuA from Lactococcus lactis transports glycine betaine upon activation by threshold values of ionic strength. In this study, the ligand binding characteristics of purified OpuA in a detergent-solubilized state and of its substrate-binding domain produced as soluble protein (OpuAC) was characterized. PRINCIPAL FINDINGS: The binding of glycine betaine to purified OpuA and OpuAC (K(D) = 4-6 microM) did not show any salt dependence or cooperative effects, in contrast to the transport activity. OpuAC is highly specific for glycine betaine and the related proline betaine. Other compatible solutes like proline and carnitine bound with affinities that were 3 to 4 orders of magnitude lower. The low affinity substrates were not noticeably transported by membrane-reconstituted OpuA. OpuAC was crystallized in an open (1.9 A) and closed-liganded (2.3 A) conformation. The binding pocket is formed by three tryptophans (Trp-prism) coordinating the quaternary ammonium group of glycine betaine in the closed-liganded structure. Even though the binding site of OpuAC is identical to that of its B. subtilis homolog, the affinity for glycine betaine is 4-fold higher. CONCLUSIONS: Ionic strength did not affect substrate binding to OpuA, indicating that regulation of transport is not at the level of substrate binding, but rather at the level of translocation. The overlap between the crystal structures of OpuAC from L.lactis and B.subtilis, comprising the classical Trp-prism, show that the differences observed in the binding affinities originate from outside of the ligand binding site.


Asunto(s)
Transportadoras de Casetes de Unión a ATP/química , Adenosina Trifosfatasas/química , Proteínas Bacterianas/química , Betaína/química , Sitios de Unión , Cristalografía por Rayos X , Ligandos , Lipoproteínas/química , Concentración Osmolar , Unión Proteica , Conformación Proteica , Solubilidad , Especificidad por Sustrato
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