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CTX-M ß-lactamases are a widespread source of resistance to ß-lactam antibiotics in Gram-negative bacteria. These enzymes readily hydrolyze penicillins and cephalosporins, including oxyimino-cephalosporins such as cefotaxime. To investigate the preference of CTX-M enzymes for cephalosporins, we examined eleven active-site residues in the CTX-M-14 ß-lactamase model system by alanine mutagenesis to assess the contribution of the residues to catalysis and specificity for the hydrolysis of the penicillin, ampicillin, and the cephalosporins cephalothin and cefotaxime. Key active site residues for class A ß-lactamases, including Lys73, Ser130, Asn132, Lys234, Thr216, and Thr235, contribute significantly to substrate binding and catalysis of penicillin and cephalosporin substrates in that alanine substitutions decrease both kcat and kcat/KM. A second group of residues, including Asn104, Tyr105, Asn106, Thr215, and Thr216, contribute only to substrate binding, with the substitutions decreasing only kcat/KM. Importantly, calculating the average effect of a substitution across the 11 active-site residues shows that the most significant impact is on cefotaxime hydrolysis while ampicillin hydrolysis is least affected, suggesting the active site is highly optimized for cefotaxime catalysis. Furthermore, we determined X-ray crystal structures for the apo-enzymes of the mutants N106A, S130A, N132A, N170A, T215A, and T235A. Surprisingly, in the structures of some mutants, particularly N106A and T235A, the changes in structure propagate from the site of substitution to other regions of the active site, suggesting that the impact of substitutions is due to more widespread changes in structure and illustrating the interconnected nature of the active site.
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Dominio Catalítico , Cefalosporinas , Resistencia a Medicamentos , Escherichia coli , beta-Lactamasas , Ampicilina/metabolismo , Ampicilina/farmacología , beta-Lactamasas/química , beta-Lactamasas/metabolismo , Catálisis , Dominio Catalítico/genética , Cefotaxima/metabolismo , Cefotaxima/farmacología , Cefalosporinas/metabolismo , Cefalosporinas/farmacología , Resistencia a Medicamentos/genética , Escherichia coli/efectos de los fármacos , Escherichia coli/metabolismo , Mutagénesis , Penicilinas/metabolismo , Penicilinas/farmacología , beta-Lactamas/metabolismo , Modelos Moleculares , Estructura Terciaria de ProteínaRESUMEN
Natural poetic speeches (i.e., proverbs, nursery rhymes, and commercial ads) with strong prosodic regularities are easily memorized by children and the harmonious acoustic patterns are suggested to facilitate their integrated sentence processing. Do children have specific neural pathways for perceiving such poetic utterances, and does their speech development benefit from it? We recorded the task-induced hemodynamic changes of 94 children aged 2 to 12 years using functional near-infrared spectroscopy (fNIRS) while they listened to poetic and non-poetic natural sentences. Seventy-three adult as controls were recruited to investigate the developmental specificity of children group. The results indicated that poetic sentences perceiving is a highly integrated process featured by a lower brain workload in both groups. However, an early activated large-scale network was induced only in the child group, coordinated by hubs for connectivity diversity. Additionally, poetic speeches evoked activation in the phonological encoding regions in the children's group rather than adult controls which decreases with children's ages. The neural responses to poetic speeches were positively linked to children's speech communication performance, especially the fluency and semantic aspects. These results reveal children's neural sensitivity to integrated speech perception which facilitate early speech development by strengthening more sophisticated language networks and the perception-production circuit.
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Percepción del Habla , Habla , Niño , Adulto , Humanos , Habla/fisiología , Percepción del Habla/fisiología , Lenguaje , Encéfalo/fisiología , Semántica , Desarrollo del LenguajeRESUMEN
The advanced electrolyte of liquid metal battery should have low melting point, low ionic solubility, low viscosity, high electric and thermal conductivities, and a suitable density between anode and cathode for declining the operating temperature and realizing the goal of saving-energy. In this study, an excellent quaternary LiF-LiCl-LiBr-LiI (9.1 : 30.0 : 21.7 : 39.2) electrolyte is refined by using thermodynamic models to balance various properties of LiX (X=F, Cl, Br, I) and meet the requirement of advanced electrolyte of liquid metal battery. The refined properties of electrolyte correspond to 2.398â g/cm3 for density, 0.286â mol% for solubility, 4.486â Ohm-1 cm-1 for ionic conductivity, and 0.609â W m-1 for thermal conductivity. The measured melting point is 609.1â K, which is lower than the current operating temperature of 723â K for the lithium-based liquid metal battery. The refined electrolyte consisted by quaternary halide molten-salt provides important references for preparing the advanced liquid metal battery.
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Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has killed more than 4 million humans globally, but there is no bona fide Food and Drug Administration-approved drug-like molecule to impede the COVID-19 pandemic. The sluggish pace of traditional therapeutic discovery is poorly suited to producing targeted treatments against rapidly evolving viruses. Here, we used an affinity-based screen of 4 billion DNA-encoded molecules en masse to identify a potent class of virus-specific inhibitors of the SARS-CoV-2 main protease (Mpro) without extensive and time-consuming medicinal chemistry. CDD-1714, the initial three-building-block screening hit (molecular weight [MW] = 542.5 g/mol), was a potent inhibitor (inhibition constant [Ki] = 20 nM). CDD-1713, a smaller two-building-block analog (MW = 353.3 g/mol) of CDD-1714, is a reversible covalent inhibitor of Mpro (Ki = 45 nM) that binds in the protease pocket, has specificity over human proteases, and shows in vitro efficacy in a SARS-CoV-2 infectivity model. Subsequently, key regions of CDD-1713 that were necessary for inhibitory activity were identified and a potent (Ki = 37 nM), smaller (MW = 323.4 g/mol), and metabolically more stable analog (CDD-1976) was generated. Thus, screening of DNA-encoded chemical libraries can accelerate the discovery of efficacious drug-like inhibitors of emerging viral disease targets.
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Proteasas 3C de Coronavirus/antagonistas & inhibidores , Proteasas 3C de Coronavirus/genética , Descubrimiento de Drogas/métodos , Inhibidores de Proteasas/química , Inhibidores de Proteasas/farmacología , SARS-CoV-2/efectos de los fármacos , SARS-CoV-2/genética , Animales , COVID-19/virología , Células Cultivadas , Proteasas 3C de Coronavirus/metabolismo , Relación Dosis-Respuesta a Droga , Activación Enzimática , Ingeniería Genética , Humanos , Modelos Moleculares , Conformación Molecular , Estructura Molecular , SARS-CoV-2/metabolismo , Relación Estructura-Actividad , Replicación Viral , Tratamiento Farmacológico de COVID-19RESUMEN
Resource-based cities (RBCs) worldwide with a single industrial structure face the double pressures of sustainable development to promote development (i.e., industrial upgrading) and mitigating carbon emissions. Although building extraregional linkages is a potential path to advance this goal, the action of these linkages still requires study since there are many contradictory conclusions in the literature. To fill this gap, the study addresses the relationship between extraregional linkages, industrial upgrading, and the low-carbon transition in RBCs from 2012 to 2019 with the help of econometric panel models with proposed variables (e.g., the coupling coordination degree of extraregional technology and investment, CCD) built from multiple new data sources. The results are as follows. First, the diversification and specialization of the local industrial structure in RBCs both reduce carbon efficiency (CE). Second, extraregional technology, on its own, does not directly enhance CE as investments do. Third, the CCD not only serves to augment CE but also acts as a mitigating factor against CE reduction during industrial diversification. Based on the above findings, distinct low-carbon transition pathways are suggested for various types of RBCs, considering their positions within the extraregional linkage network.
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Carbono , Ciudades , Desarrollo Sostenible , Inversiones en Salud , TecnologíaRESUMEN
Vision is a key source of information input for humans, which involves various cognitive functions and a great range of neural networks inside and beyond the visual cortex. There has been increasing observation that the cognitive outcomes after a brain lesion cannot be well predicted by the attributes of the lesion itself but are influenced by the functional network plasticity. However, the mechanisms of impaired or preserved visual cognition have not been probed from direct function-execution conditions and few works have observed it on whole-brain dynamic networks. We used high-resolution electroencephalogram recordings from 25 patients with brain tumors to track the dynamical patterns of functional reorganization in visual processing tasks with multilevel complexity. By comparing with 24 healthy controls, increased cortical responsiveness as functional compensation was identified in the early phase of processing, which was highly localized to the visual cortex and functional networks and less relevant to the tumor position. Besides, a spreading wide enhancement in whole-brain functional connectivity was elicited by the visual word-recognition task. Enhanced early rapid-onset cortical compensation in the local functional networks may contribute to largely preserved basic vision functions, and higher-cognitive tasks are vulnerable to impairment but with high sensitivity of functional plasticity being elicited.
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Neoplasias Encefálicas , Corteza Visual , Encéfalo , Mapeo Encefálico , Neoplasias Encefálicas/diagnóstico por imagen , Cognición , Humanos , Imagen por Resonancia Magnética , Redes Neurales de la Computación , Vías Nerviosas , Percepción VisualRESUMEN
The H+/Ca2+ (calcium ion) antiporter (CAX) plays an important role in maintaining cellular Ca2+ homeostasis in bacteria, yeast, and plants by promoting Ca2+ efflux across the cell membranes. However, how CAX facilitates Ca2+ balance in response to dynamic cytosolic Ca2+ perturbations is unknown. Here, we identified a type of Ca2+ "mini-sensor" in YfkE, a bacterial CAX homolog from Bacillus subtilis. The mini-sensor is formed by six tandem carboxylate residues within the transmembrane (TM)5-6 loop on the intracellular membrane surface. Ca2+ binding to the mini-sensor triggers the transition of the transport mode of YfkE from a high-affinity to a low-affinity state. Molecular dynamics simulation and fluorescence resonance energy transfer analysis suggest that Ca2+ binding to the mini-sensor causes an adjacent segment, namely, the exchanger inhibitory peptide (XIP), to move toward the Ca2+ translocation pathway to interact with TM2a in an inward-open cavity. The specific interaction was demonstrated with a synthetic peptide of the XIP, which inhibits YfkE transport and interrupts conformational changes mediated by the mini-sensor. By comparing the apo and Ca2+-bound CAX structures, we propose the following Ca2+ transport regulatory mechanism of YfkE: Ca2+ binding to the mini-sensor induces allosteric conformational changes in the Ca2+ translocation pathway via the XIP, resulting in a rearrangement of the Ca2+-binding transport site in the midmembrane. Since the Ca2+ mini-sensor and XIP sequences are also identified in other CAX homologs and/or Ca2+ transporters, including the mammalian Na+/Ca2+ exchanger (NCX), our study provides a regulatory mechanism for the Ca2+/cation transporter superfamily.
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Antiportadores/metabolismo , Bacillus subtilis/metabolismo , Proteínas Bacterianas/metabolismo , Calcio/metabolismo , Citoplasma/metabolismo , Escherichia coli/metabolismo , Intercambiador de Sodio-Calcio/metabolismo , Secuencia de Aminoácidos , Antiportadores/genética , Bacillus subtilis/genética , Proteínas Bacterianas/química , Proteínas Bacterianas/genética , Membrana Celular/metabolismo , Escherichia coli/genética , Mutación , Conformación Proteica , Homología de Secuencia , Intercambiador de Sodio-Calcio/genéticaRESUMEN
Aryl sulfones and aryl sulfonamides are of great importance in organic synthesis and medicinal chemistry. Although ortho-C-H functionalization of aryl sulfonyl compounds has been extensively explored, the functionalization of remote meta- and para-C-H bonds is very rare. Herein, we report a tunable meta- and para-selective C-H borylation of aryl sulfonyl compounds enabled by computationally designed ligands and iridium catalyst. This method is capable of accommodating a broad range of substrates under mild reaction conditions. Gram-scale preparation can be achieved with iridium catalyst loading as low as 0.1â mol%. As the introduced boronate group can be easily converted into many other groups, our method provides a general solution to installing functional groups at either meta- or para-position of aryl sulfones and aryl sulfonamides with good to excellent selectivity.
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Aromatic ammonium and phosphonium salts are important synthetic intermediates and multifunctional materials, but para-selective functionalization of the aromatic salts remains a challenge. Here we develop an ionic ligand based on our newly designed "biphenyl-phenanthroline" skeleton and realize the Ir-catalyzed para-selective C-H borylation of seven types of aromatic quaternary ammonium and phosphonium salts. Gram-scale transformation, late-stage elaboration for drug molecule, and diversification of borylated products demonstrate the potential utility of this reaction. The mechanistic studies and computational analysis elucidate the origin of para-selectivity.
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Lys234 is one of the residues present in class A ß-lactamases that is under selective pressure due to antibiotic use. Located adjacent to proton shuttle residue Ser130, it is suggested to play a role in proton transfer during catalysis of the antibiotics. The mechanism underpinning how substitutions in this position modulate inhibitor efficiency and substrate specificity leading to drug resistance is unclear. The K234R substitution identified in several inhibitor-resistant ß-lactamase variants is associated with decreased potency of the inhibitor clavulanic acid, which is used in combination with amoxicillin to overcome ß-lactamase-mediated antibiotic resistance. Here we show that for CTX-M-14 ß-lactamase, whereas Lys234 is required for hydrolysis of cephalosporins such as cefotaxime, either lysine or arginine is sufficient for hydrolysis of ampicillin. Further, by determining the acylation and deacylation rates for cefotaxime hydrolysis, we show that both rates are fast, and neither is rate-limiting. The K234R substitution causes a 1500-fold decrease in the cefotaxime acylation rate but a 5-fold increase in kcat for ampicillin, suggesting that the K234R enzyme is a good penicillinase but a poor cephalosporinase due to slow acylation. Structural results suggest that the slow acylation by the K234R enzyme is due to a conformational change in Ser130, and this change also leads to decreased inhibition potency of clavulanic acid. Because other inhibitor resistance mutations also act through changes at Ser130 and such changes drastically reduce cephalosporin but not penicillin hydrolysis, we suggest that clavulanic acid paired with an oxyimino-cephalosporin rather than penicillin would impede the evolution of resistance.
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Antibacterianos/farmacología , Mutación , Protones , Resistencia betalactámica/genética , Inhibidores de beta-Lactamasas/farmacología , beta-Lactamasas/química , beta-Lactamasas/metabolismo , Dominio Catalítico , Escherichia coli/enzimología , Escherichia coli/crecimiento & desarrollo , Mutagénesis Sitio-Dirigida , Conformación Proteica , Especificidad por Sustrato , beta-Lactamasas/genéticaRESUMEN
Secretory phospholipases A2 (sPLA2s) are potent components of mammalian innate-immunity antibacterial mechanisms. sPLA2 enzymes attack bacteria by hydrolyzing bacterial membrane phospholipids, causing membrane disorganization and cell lysis. However, most Gram-negative bacteria are naturally resistant to sPLA2 Here we report a novel resistance mechanism to mammalian sPLA2 in Escherichia coli, mediated by a phospholipid repair system consisting of the lysophospholipid transporter LplT and the acyltransferase Aas in the cytoplasmic membrane. Mutation of the lplT or aas gene abolished bacterial lysophospholipid acylation activity and drastically increased bacterial susceptibility to the combined actions of inflammatory fluid components and sPLA2, resulting in bulk phospholipid degradation and loss of colony-forming ability. sPLA2-mediated hydrolysis of the three major bacterial phospholipids exhibited distinctive kinetics and deacylation of cardiolipin to its monoacyl-derivative closely paralleled bacterial death. Characterization of the membrane envelope in lplT- or aas-knockout mutant bacteria revealed reduced membrane packing and disruption of lipid asymmetry with more phosphatidylethanolamine present in the outer leaflet of the outer membrane. Moreover, modest accumulation of lysophospholipids in these mutant bacteria destabilized the inner membrane and rendered outer membrane-depleted spheroplasts much more sensitive to sPLA2 These findings indicated that LplT/Aas inactivation perturbs both the outer and inner membranes by bypassing bacterial membrane maintenance mechanisms to trigger specific interfacial activation of sPLA2 We conclude that the LplT/Aas system is important for maintaining the integrity of the membrane envelope in Gram-negative bacteria. Our insights may help inform new therapeutic strategies to enhance host sPLA2 antimicrobial activity.
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Aciltransferasas/metabolismo , Membrana Celular/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/citología , Escherichia coli/fisiología , Interacciones Huésped-Patógeno , Fosfolipasas A2/metabolismo , Proteínas de Transferencia de Fosfolípidos/metabolismo , Fosfolípidos/metabolismo , Aciltransferasas/deficiencia , Animales , Activación Enzimática , Escherichia coli/enzimología , Proteínas de Transferencia de Fosfolípidos/deficienciaRESUMEN
This study aimed to verify the differentially expressed miRNAs (microRNAs) in hemangioma, and explore their roles in the pathogenesis of hemangioma in vivo and ex vivo. Real-time polymerase chain reaction (PCR) and western blot were used to measure reported differentially expressed miRNAs and their potential targets. In-silicon analysis and luciferase assay were conducted to find the target of miR-15a and miR-205. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and flowcytometry were performed to examine the effect of dysregulation of miR-15a and miR-205 on the proliferation and apoptosis of endothelial cells. Among all candidate miRNAs, only miR-205 level was significantly downregulated whereas miR-15a was evidently upregulated in the hemangioma group. Accordingly, AKT3 was validated to be the direct target of miR-15a and miR-205. Using real-time PCR, the level of AKT1 was much higher in hemangioma group, whereas level of AKT3 was much lower in the hemangioma group, and in general expression level of ATK was upregulated in the hemangioma group. Furthermore, the ATK1 level of cells transfected with miR-205 mimics and ATK1 siRNA was substantially downregulated, and anti-miR-205 mimic significantly improved the level of AKT1, and meanwhile the level of ATK3 and PTEN were remarkably suppressed after transfection with miR-15a mimics and ATK3 siRNA, whereas notably overexpressed after introduction of anti-miR-15a. And miR-15a, AKT3 siRNA and anti-miR-205 evidently induced viability, and miR-205, AKT1 siRNA, and anti-miR-15a obviously promoted apoptosis of cells. CONCLUSION: miR-15a and miR-205 had different expression in hemangioma, may be novel therapeutic targets in the treatment of hemangioma by targeting AKT3 and AKT1.
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Hemangioma/genética , MicroARNs/metabolismo , Proteínas Proto-Oncogénicas c-akt/biosíntesis , Proliferación Celular/genética , Preescolar , Regulación hacia Abajo , Células Endoteliales/metabolismo , Femenino , Regulación Neoplásica de la Expresión Génica/genética , Hemangioma/metabolismo , Humanos , Lactante , Recién Nacido , Masculino , Regulación hacia ArribaRESUMEN
BACKGROUND: It is usually difficult to identify stroke pathogenesis for single lenticulostriate infarction with nonstenotic middle cerebral artery (MCA). Our aim is to differentiate the two pathogeneses, non-branch atheromatous small vessel disease and branch atheromatous disease (BAD) by high-resolution magnetic resonance imaging (HR-MRI). METHODS: Thirty-two single lenticulostriate infarction patients with nonstenotic MCA admitted to the China-Japan Friendship Hospital from December 2014 to August 2017 were enrolled for retrospective analysis. National Institutes of Health Stroke Scale (NIHSS), modified Rankin Scale (mRS), atherosclerotic risk factors, imaging features, and the characteristic of MCA vessel wall in HR-MRI were evaluated. RESULTS: MCA plaques were detected in 15(46.9%) patients which implied BAD and 8 of 15 (53.3%) patients had plaques location in upper dorsal side of the vessel wall. Patients with HR-MRI identified plaques had a significantly larger infarction lesion length (1.95 ± 0.86 cm versus 1.38 ± 0.55 cm; P = 0.031) and larger lesion volume (2.95 ± 3.94 cm3 versus 0.90 ± 0.94 cm3; P = 0.027) than patients without plaques. Patients with HR-MRI identified plaques had a significant higher percentage of proximal lesions than patients without plaques (P = 0.055). However, according to the location of MCA plaques, there were no significant differences in terms of imaging features, NIHSS and mRS. CONCLUSION: We demonstrated high frequency of MCA atheromatous plaques visualized in single lenticulostriate infarction patients with nonstenotic MCA by using HR-MRI. Patients with HR-MRI identified plaque presented larger infarction lesions and more proximal lesions than patients without plaque, which were consistent with imaging features of BAD. HR-MRI is an important and effective tool for identifying stroke etiology in patients with nonstenotic MCA.
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Infarto de la Arteria Cerebral Media/diagnóstico por imagen , Infarto de la Arteria Cerebral Media/etiología , Arteria Cerebral Media/diagnóstico por imagen , Placa Aterosclerótica/diagnóstico por imagen , Anciano , China , Femenino , Humanos , Infarto de la Arteria Cerebral Media/patología , Japón , Angiografía por Resonancia Magnética/métodos , Imagen por Resonancia Magnética/métodos , Masculino , Persona de Mediana Edad , Arteria Cerebral Media/patología , Placa Aterosclerótica/patología , Estudios Retrospectivos , Factores de RiesgoRESUMEN
PgpB belongs to the lipid phosphate phosphatase protein family and is one of three bacterial integral membrane phosphatases catalyzing dephosphorylation of phosphatidylglycerol phosphate (PGP) to generate phosphatidylglycerol. Although the structure of its apo form became recently available, the mechanisms of PgpB substrate binding and catalysis are still unclear. We found that PgpB was inhibited by phosphatidylethanolamine (PE) in a competitive mode in vitro Here we report the crystal structure of the lipid-bound form of PgpB. The structure shows that a PE molecule is stabilized in a membrane-embedded tunnel formed by TM3 and the "PSGH" fingerprint peptide near the catalytic site, providing structural insight into PgpB substrate binding mechanism. Noteworthy, in silico docking of varied lipid phosphates exhibited similar substrate binding modes to that of PE, and the residues in the lipid tunnel appear to be important for PgpB catalysis. The catalytic triad in the active site is essential for dephosphorylating substrates lysophosphatidic acid, phosphatidic acid, or sphingosine-1-phosphate but surprisingly not for the native substrate PGP. Remarkably, residue His-207 alone is sufficient to hydrolyze PGP, indicating a specific catalytic mechanism for PgpB in PG biosynthesis. We also identified two novel sensor residues, Lys-93 and Lys-97, on TM3. Our data show that Lys-97 is essential for the recognition of lyso-form substrates. Modification at the Lys-93 position may alter substrate specificity of lipid phosphate phosphatase proteins in prokaryotes versus eukaryotes. These studies reveal new mechanisms of lipid substrate selection and catalysis by PgpB and suggest that the enzyme rests in a PE-stabilized state in the bilayer.
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Membrana Celular/enzimología , Proteínas de Escherichia coli/química , Escherichia coli/enzimología , Lisofosfolípidos/química , Fosfatidato Fosfatasa/química , Esfingosina/análogos & derivados , Catálisis , Dominio Catalítico , Membrana Celular/genética , Membrana Celular/metabolismo , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Lisofosfolípidos/genética , Lisofosfolípidos/metabolismo , Fosfatidato Fosfatasa/genética , Fosfatidato Fosfatasa/metabolismo , Esfingosina/química , Esfingosina/genética , Esfingosina/metabolismo , Especificidad por SustratoRESUMEN
Lysophospholipids (LPLs) are metabolic intermediates in bacterial phospholipid turnover. Distinct from their diacyl counterparts, these inverted cone-shaped molecules share physical characteristics of detergents, enabling modification of local membrane properties such as curvature. The functions of LPLs as cellular growth factors or potent lipid mediators have been extensively demonstrated in eukaryotic cells but are still undefined in bacteria. In the envelope of Gram-negative bacteria, LPLs are derived from multiple endogenous and exogenous sources. Although several flippases that move non-glycerophospholipids across the bacterial inner membrane were characterized, lysophospholipid transporter LplT appears to be the first example of a bacterial protein capable of facilitating rapid retrograde translocation of lyso forms of glycerophospholipids across the cytoplasmic membrane in Gram-negative bacteria. LplT transports lyso forms of the three bacterial membrane phospholipids with comparable efficiency, but excludes other lysolipid species. Once a LPL is flipped by LplT to the cytoplasmic side of the inner membrane, its diacyl form is effectively regenerated by the action of a peripheral enzyme, acyl-ACP synthetase/LPL acyltransferase (Aas). LplT-Aas also mediates a novel cardiolipin remodeling by converting its two lyso derivatives, diacyl or deacylated cardiolipin, to a triacyl form. This coupled remodeling system provides a unique bacterial membrane phospholipid repair mechanism. Strict selectivity of LplT for lyso lipids allows this system to fulfill efficient lipid repair in an environment containing mostly diacyl phospholipids. A rocker-switch model engaged by a pair of symmetric ion-locks may facilitate alternating substrate access to drive LPL flipping into bacterial cells. This article is part of a Special Issue entitled: Bacterial Lipids edited by Russell E. Bishop.
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Pared Celular/metabolismo , Bacterias Gramnegativas/metabolismo , Lipogénesis , Lisofosfolípidos/biosíntesis , Proteínas de Transferencia de Fosfolípidos/metabolismo , Proteínas Bacterianas/química , Proteínas Bacterianas/metabolismo , Transporte Biológico , Ligasas de Carbono-Azufre/química , Ligasas de Carbono-Azufre/metabolismo , Lisofosfolípidos/química , Proteínas de Transferencia de Fosfolípidos/química , Transducción de Señal , Especificidad por SustratoRESUMEN
Understanding how changing climate and cultivars influence crop phenology and potential yield is essential for crop adaptation to future climate change. In this study, crop and daily weather data collected from six sites across the North China Plain were used to drive a crop model to analyze the impacts of climate change and cultivar development on the phenology and production of winter wheat from 1981 to 2005. Results showed that both the growth period (GP) and the vegetative growth period (VGP) decreased during the study period, whereas changes in the reproductive growth period (RGP) either increased slightly or had no significant trend. Although new cultivars could prolong the winter wheat phenology (0.3â¼3.8 days per decade for GP), climate warming impacts were more significant and mainly accounted for the changes. The harvest index and kernel number per stem weight have significantly increased. Model simulation indicated that the yield of winter wheat exhibited increases (5.0â¼19.4%) if new cultivars were applied. Climate change demonstrated a negative effect on winter wheat yield as suggested by the simulation driven by climate data only (-3.3 to -54.8 kg ha(-1) year(-1), except for Lushi). Results of this study also indicated that winter wheat cultivar development can compensate for the negative effects of future climatic change.
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Cambio Climático , Modelos Teóricos , Triticum/crecimiento & desarrollo , China , Clima , Estaciones del AñoRESUMEN
PURPOSE: The purpose of this study was to thoroughly analyze postoperative consonant errors by tongue cancer (TC) patients with speech disorders and also to investigate the correlation between the pathological factors and the speech performance using our Consonant-based Articulation Assessment Battery (CAAB). METHOD: The participants were 57 monolingual Mandarin TC patients (26 women, 31 men) after surgery (aged 20-80 years). All participants were literate and had normal vision and hearing, enabling them to comprehend and comply with our instructions. In order to quickly evaluate their articulation performance based on the place and manner of articulation, they were instructed to pronounce the characters in CAAB. The analysis removed speech samples impacted by speakers' dialects, while recording and documenting all other responses. RESULTS: The study uncovered a significant correlation between pathological factors (e.g., size of tongue resection, specific resection site, and tumor size) and the accuracy of consonant articulation. Furthermore, tongue damage predominantly impacts the place of articulation (63.85%) than the manner of articulation (20.78%). The damage in the anterior part of the tongue has the most prominent influence on consonant production. CONCLUSIONS: CAAB can fast capture the idiosyncratic characteristics of speech production by TC patients, and the articulation deficits are quite different from other types of organic or nonorganic speech disorders, for example, cleft lip and cleft palate. Hence, CAAB can be designated as an assessment tool for articulation disorders caused by stomatognathic damages. Our findings also shed light on the possible oral cancer surgery plan and the postoperative speech rehabilitation training.
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BACKGROUND: Parkinson's disease (PD) is a neurodegenerative disorder characterized by the degeneration of dopaminergic neurons in the substantia nigra (SN). Activation of the neuroinflammatory response has a pivotal role in PD. Mesenchymal stem cells (MSCs) have emerged as a promising therapeutic approach for various nerve injuries, but there are limited reports on their use in PD and the underlying mechanisms remain unclear. METHODS: We investigated the effects of clinical-grade hypoxia-preconditioned olfactory mucosa (hOM)-MSCs on neural functional recovery in both PD models and patients, as well as the preventive effects on mouse models of PD. To assess improvement in neuroinflammatory response and neural functional recovery induced by hOM-MSCs exposure, we employed single-cell RNA sequencing (scRNA-seq), assay for transposase accessible chromatin with high-throughput sequencing (ATAC-seq) combined with full-length transcriptome isoform-sequencing (ISO-seq), and functional assay. Furthermore, we present the findings from an initial cohort of patients enrolled in a phase I first-in-human clinical trial evaluating the safety and efficacy of intraspinal transplantation of hOM-MSC transplantation into severe PD patients. RESULTS: A functional assay identified that transforming growth factor-ß1 (TGF-ß1), secreted from hOM-MSCs, played a critical role in modulating mitochondrial function recovery in dopaminergic neurons. This effect was achieved through improving microglia immune regulation and autophagy homeostasis in the SN, which are closely associated with neuroinflammatory responses. Mechanistically, exposure to hOM-MSCs led to an improvement in neuroinflammation and neural function recovery partially mediated by TGF-ß1 via activation of the anaplastic lymphoma kinase/phosphatidylinositol-3-kinase/protein kinase B (ALK/PI3K/Akt) signaling pathway in microglia located in the SN of PD patients. Furthermore, intraspinal transplantation of hOM-MSCs improved the recovery of neurologic function and regulated the neuroinflammatory response without any adverse reactions observed in patients with PD. CONCLUSIONS: These findings provide compelling evidence for the involvement of TGF-ß1 in mediating the beneficial effects of hOM-MSCs on neural functional recovery in PD. Treatment and prevention of hOM-MSCs could be a promising and effective neuroprotective strategy for PD. Additionally, TGF-ß1 may be used alone or combined with hOM-MSCs therapy for treating PD.
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Modelos Animales de Enfermedad , Células Madre Mesenquimatosas , Mucosa Olfatoria , Enfermedad de Parkinson , Factor de Crecimiento Transformador beta1 , Animales , Femenino , Humanos , Masculino , Ratones , Persona de Mediana Edad , Trasplante de Células Madre Mesenquimatosas/métodos , Enfermedad de Parkinson/complicaciones , Enfermedad de Parkinson/terapia , Recuperación de la Función , Factor de Crecimiento Transformador beta1/metabolismoRESUMEN
The Escherichia coli MacAB-TolC transporter has been implicated in efflux of macrolide antibiotics and secretion of enterotoxin STII. In this study, we found that purified MacA, a periplasmic membrane fusion protein, contains one tightly bound rough core lipopolysaccharide (R-LPS) molecule per MacA molecule. R-LPS was bound specifically to MacA protein with affinity exceeding that of polymyxin B. Sequence analyses showed that MacA contains two high-density clusters of positively charged amino acid residues located in the cytoplasmic N-terminal domain and the periplasmic C-terminal domain. Substitutions in the C-terminal cluster reducing the positive-charge density completely abolished binding of R-LPS. At the same time, these substitutions significantly reduced the functionality of MacA in the protection of E. coli against macrolides in vivo and in the in vitro MacB ATPase stimulation assays. Taken together, our results suggest that R-LPS or a similar glycolipid is a physiological substrate of MacAB-TolC.
Asunto(s)
Transportadoras de Casetes de Unión a ATP/metabolismo , Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Lipopolisacáridos/metabolismo , Transportadoras de Casetes de Unión a ATP/genética , Proteínas de Escherichia coli/genética , Regulación Bacteriana de la Expresión Génica/fisiología , Lipopolisacáridos/química , Mutagénesis Sitio-Dirigida , Unión Proteica , Estructura Terciaria de ProteínaRESUMEN
MacB is a founding member of the Macrolide Exporter family of transporters belonging to the ATP-Binding Cassette superfamily. These proteins are broadly represented in genomes of both Gram-positive and Gram-negative bacteria and are implicated in virulence and protection against antibiotics and peptide toxins. MacB transporter functions together with MacA, a periplasmic membrane fusion protein, which stimulates MacB ATPase. In Gram-negative bacteria, MacA is believed to couple ATP hydrolysis to transport of substrates across the outer membrane through a TolC-like channel. In this study, we report a real-time analysis of concurrent ATP hydrolysis and assembly of MacAB-TolC complex. MacB binds nucleotides with a low millimolar affinity and fast on- and off-rates. In contrast, MacA-MacB complex is formed with a nanomolar affinity, which further increases in the presence of ATP. Our results strongly suggest that association between MacA and MacB is stimulated by ATP binding to MacB but remains unchanged during ATP hydrolysis cycle. We also found that the large periplasmic loop of MacB plays the major role in coupling reactions separated in two different membranes. This loop is required for MacA-dependent stimulation of MacB ATPase and at the same time, contributes to recruitment of TolC into a trans-envelope complex.