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1.
Nat Commun ; 11(1): 4557, 2020 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-32917908

RESUMO

Why metalloenzymes often show dramatic changes in their catalytic activity when subjected to chemically similar but non-native metal substitutions is a long-standing puzzle. Here, we report on the catalytic roles of metal ions in a model metalloenzyme system, human carbonic anhydrase II (CA II). Through a comparative study on the intermediate states of the zinc-bound native CA II and non-native metal-substituted CA IIs, we demonstrate that the characteristic metal ion coordination geometries (tetrahedral for Zn2+, tetrahedral to octahedral conversion for Co2+, octahedral for Ni2+, and trigonal bipyramidal for Cu2+) directly modulate the catalytic efficacy. In addition, we reveal that the metal ions have a long-range (~10 Å) electrostatic effect on restructuring water network in the active site. Our study provides evidence that the metal ions in metalloenzymes have a crucial impact on the catalytic mechanism beyond their primary chemical properties.


Assuntos
Anidrases Carbônicas/química , Íons/química , Metaloproteínas/química , Metais/química , Sítios de Ligação , Anidrase Carbônica II/química , Anidrase Carbônica II/metabolismo , Anidrases Carbônicas/metabolismo , Catálise , Domínio Catalítico , Cobalto/química , Cobre/química , Cristalografia por Raios X , Humanos , Íons/metabolismo , Cinética , Metaloproteínas/metabolismo , Metais/metabolismo , Modelos Moleculares , Níquel/química , Conformação Proteica , Relação Estrutura-Atividade , Especificidade por Substrato , Zinco/química
2.
Chemosphere ; 260: 127541, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32688311

RESUMO

The present study explores the effect of ethylene diamine disuccinic acid (EDDS) and gibberellic acid (GA) application on the phytoextraction of copper and zinc ions by Lolium perenne. When Cu was individually applied, accumulation diminished over time with little translocation from roots to shoots. In contrast, Zn accumulation and damage to roots rapidly increased over 3 days with increase in Zn translocation to shoots. Co-application of Zn to Cu amended treatments enhanced Cu concentration in shoots. For the CuEDDS application, EDDS significantly increased Cu accumulation and the damage to root increased over time, while gibberellic acid applied with Cu and Zn generally lowered metal uptake and decreased cell membrane damage. The application of EDDS and GA-EDDS, by themselves or with Cu and Zn, lowered transpiration and increased translocation, while GA increased transpiration but decreased translocation. EDDS application typically increased metal ion uptake by causing more cell damage, while GA typically lowered the damage and decreased metal uptake even though the transpiration increased over time and plant growth occurred. Furthermore, the behaviour of metal uptake changed over time and, for some treatments, the short-term and long-term response differed greatly. These results show that EDDS can be successfully used in phytoextraction of both Cu and Zn ions by Lolium perenne while GA can resist damage and protect against plant stress.


Assuntos
Biodegradação Ambiental , Etilenodiaminas/química , Giberelinas/química , Lolium/metabolismo , Poluentes do Solo/metabolismo , Transporte Biológico , Cobre/metabolismo , Etilenos , Íons/metabolismo , Raízes de Plantas/metabolismo , Succinatos/metabolismo , Zinco/metabolismo
3.
Nat Commun ; 11(1): 3024, 2020 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-32541684

RESUMO

The canonical mechanistic model explaining potassium channel gating is of a conformational change that alternately dilates and constricts a collar-like intracellular entrance to the pore. It is based on the premise that K+ ions maintain a complete hydration shell while passing between the transmembrane cavity and cytosol, which must be accommodated. To put the canonical model to the test, we locked the conformation of a Kir K+ channel to prevent widening of the narrow collar. Unexpectedly, conduction was unimpaired in the locked channels. In parallel, we employed all-atom molecular dynamics to simulate K+ ions moving along the conduction pathway between the lower cavity and cytosol. During simulations, the constriction did not significantly widen. Instead, transient loss of some water molecules facilitated K+ permeation through the collar. The low free energy barrier to partial dehydration in the absence of conformational change indicates Kir channels are not gated by the canonical mechanism.


Assuntos
Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/metabolismo , Potássio/metabolismo , Citosol/química , Citosol/metabolismo , Condutividade Elétrica , Impedância Elétrica , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/química , Canais de Potássio Corretores do Fluxo de Internalização Acoplados a Proteínas G/genética , Humanos , Transporte de Íons , Íons/química , Íons/metabolismo , Simulação de Dinâmica Molecular , Potássio/química , Conformação Proteica , Água/metabolismo
4.
J Virol ; 94(13)2020 06 16.
Artigo em Inglês | MEDLINE | ID: mdl-32295925

RESUMO

Fusion with, and subsequent entry into, the host cell is one of the critical steps in the life cycle of enveloped viruses. For Middle East respiratory syndrome coronavirus (MERS-CoV), the spike (S) protein is the main determinant of viral entry. Proteolytic cleavage of the S protein exposes its fusion peptide (FP), which initiates the process of membrane fusion. Previous studies on the related severe acute respiratory syndrome coronavirus (SARS-CoV) FP have shown that calcium ions (Ca2+) play an important role in fusogenic activity via a Ca2+ binding pocket with conserved glutamic acid (E) and aspartic acid (D) residues. SARS-CoV and MERS-CoV FPs share a high sequence homology, and here, we investigated whether Ca2+ is required for MERS-CoV fusion by screening a mutant array in which E and D residues in the MERS-CoV FP were substituted with neutrally charged alanines (A). Upon verifying mutant cell surface expression and proteolytic cleavage, we tested their ability to mediate pseudoparticle (PP) infection of host cells in modulating Ca2+ environments. Our results demonstrate that intracellular Ca2+ enhances MERS-CoV wild-type (WT) PP infection by approximately 2-fold and that E891 is a crucial residue for Ca2+ interaction. Subsequent electron spin resonance (ESR) experiments revealed that this enhancement could be attributed to Ca2+ increasing MERS-CoV FP fusion-relevant membrane ordering. Intriguingly, isothermal calorimetry showed an approximate 1:1 MERS-CoV FP to Ca2+ ratio, as opposed to an 1:2 SARS-CoV FP to Ca2+ ratio, suggesting significant differences in FP Ca2+ interactions of MERS-CoV and SARS-CoV FP despite their high sequence similarity.IMPORTANCE Middle East respiratory syndrome coronavirus (MERS-CoV) is a major emerging infectious disease with zoonotic potential and has reservoirs in dromedary camels and bats. Since its first outbreak in 2012, the virus has repeatedly transmitted from camels to humans, with 2,468 confirmed cases causing 851 deaths. To date, there are no efficacious drugs and vaccines against MERS-CoV, increasing its potential to cause a public health emergency. In order to develop novel drugs and vaccines, it is important to understand the molecular mechanisms that enable the virus to infect host cells. Our data have found that calcium is an important regulator of viral fusion by interacting with negatively charged residues in the MERS-CoV FP region. This information can guide therapeutic solutions to block this calcium interaction and also repurpose already approved drugs for this use for a fast response to MERS-CoV outbreaks.


Assuntos
Cálcio/metabolismo , Infecções por Coronavirus/metabolismo , Infecções por Coronavirus/virologia , Interações Hospedeiro-Patógeno , Íons/metabolismo , Fusão de Membrana , Coronavírus da Síndrome Respiratória do Oriente Médio/fisiologia , Internalização do Vírus , Sequência de Aminoácidos , Substituição de Aminoácidos , Animais , Linhagem Celular , Chlorocebus aethiops , Humanos , Coronavírus da Síndrome Respiratória do Oriente Médio/patogenicidade , Modelos Moleculares , Mutação , Ligação Proteica , Proteólise , Glicoproteína da Espícula de Coronavírus/química , Glicoproteína da Espícula de Coronavírus/genética , Glicoproteína da Espícula de Coronavírus/metabolismo , Relação Estrutura-Atividade , Células Vero , Virulência , Montagem de Vírus
5.
PLoS Comput Biol ; 16(3): e1007605, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32119665

RESUMO

Intracellular calcium ([Ca2+]i) is a basic and ubiquitous cellular signal controlling a wide variety of biological processes. A remarkable example is the steering of sea urchin spermatozoa towards the conspecific egg by a spatially and temporally orchestrated series of [Ca2+]i spikes. Although this process has been an experimental paradigm for reproduction and sperm chemotaxis studies, the composition and regulation of the signalling network underlying the cytosolic calcium fluctuations are hitherto not fully understood. Here, we used a differential equations model of the signalling network to assess which set of channels can explain the characteristic envelope and temporal organisation of the [Ca2+]i-spike trains. The signalling network comprises an initial membrane hyperpolarisation produced by an Upstream module triggered by the egg-released chemoattractant peptide, via receptor activation, cGMP synthesis and decay. Followed by downstream modules leading to intraflagellar pH (pHi), voltage and [Ca2+]i fluctuations. The Upstream module outputs were fitted to kinetic data on cGMP activity and early membrane potential changes measured in bulk cell populations. Two candidate modules featuring voltage-dependent Ca2+-channels link these outputs to the downstream dynamics and can independently explain the typical decaying envelope and the progressive spacing of the spikes. In the first module, [Ca2+]i-spike trains require the concerted action of a classical CaV-like channel and a potassium channel, BK (Slo1), whereas the second module relies on pHi-dependent CatSper dynamics articulated with voltage-dependent neutral sodium-proton exchanger (NHE). We analysed the dynamics of these two modules alone and in mixed scenarios. We show that the [Ca2+]i dynamics observed experimentally after sustained alkalinisation can be reproduced by a model featuring the CatSper and NHE module but not by those including the pH-independent CaV and BK module or proportionate mixed scenarios. We conclude in favour of the module containing CatSper and NHE and highlight experimentally testable predictions that would corroborate this conclusion.


Assuntos
Canais de Cálcio/metabolismo , Ouriços-do-Mar/metabolismo , Espermatozoides/fisiologia , Animais , Cálcio/metabolismo , Sinalização do Cálcio/fisiologia , Quimiotaxia/fisiologia , Biologia Computacional/métodos , Íons/metabolismo , Masculino , Potenciais da Membrana/fisiologia , Modelos Teóricos , Transdução de Sinais , Motilidade Espermática/fisiologia
6.
Arch Microbiol ; 202(6): 1407-1417, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32173773

RESUMO

Pseudomonas spp. are the main producers of rhamnolipids. These products have applications in pharmaceuticals, cosmetics, food industry and bioremediation. The biosynthesis of rhamnolipids is influenced by nutrient composition, pH and temperature. In this study, the impact of nutrients on the expression levels of rhamnolipid synthesis genes was evaluated in P. aeruginosa ATCC 15442. Glucose and glycerol were used as carbon sources; while, NaNO3, NH4NO3 and yeast extract/peptone were employed as nitrogen sources. The effect of different concentrations of Fe2+ and Fe3+ on rhamnolipid synthesis genes was also evaluated. Highest biosurfactant production was obtained in minimal medium supplemented with glucose, NaNO3 and Fe2+. Two rhamnolipid synthesis genes, rhlA and rhlB, were amplified with PCR. CapLC ESI-Ion trap-MS/MS detected only mono-rhamnolipid Rha-C10-C10 in the extract. Although similar induction levels were recorded in the presence of 0.05 g/L iron ions, the presence of Fe2+ resulted in higher expression levels than Fe3+ at concentrations equivalent to 0.025 and 0.075 g/L.


Assuntos
Carbono/metabolismo , Glicolipídeos/biossíntese , Ferro/metabolismo , Nitrogênio/metabolismo , Pseudomonas aeruginosa/metabolismo , Glucose/metabolismo , Glicerol/metabolismo , Íons/metabolismo , Nitratos/metabolismo , Peptonas/metabolismo , Pseudomonas aeruginosa/genética , Tensoativos/química , Tensoativos/metabolismo , Espectrometria de Massas em Tandem
7.
Proc Natl Acad Sci U S A ; 117(11): 5861-5872, 2020 03 17.
Artigo em Inglês | MEDLINE | ID: mdl-32123101

RESUMO

The cytoskeletal protein actin polymerizes into filaments that are essential for the mechanical stability of mammalian cells. In vitro experiments showed that direct interactions between actin filaments and lipid bilayers are possible and that the net charge of the bilayer as well as the presence of divalent ions in the buffer play an important role. In vivo, colocalization of actin filaments and divalent ions are suppressed, and cells rely on linker proteins to connect the plasma membrane to the actin network. Little is known, however, about why this is the case and what microscopic interactions are important. A deeper understanding is highly beneficial, first, to obtain understanding in the biological design of cells and, second, as a possible basis for the building of artificial cortices for the stabilization of synthetic cells. Here, we report the results of coarse-grained molecular dynamics simulations of monomeric and filamentous actin in the vicinity of differently charged lipid bilayers. We observe that charges on the lipid head groups strongly determine the ability of actin to adsorb to the bilayer. The inclusion of divalent ions leads to a reversal of the binding affinity. Our in silico results are validated experimentally by reconstitution assays with actin on lipid bilayer membranes and provide a molecular-level understanding of the actin-membrane interaction.


Assuntos
Citoesqueleto de Actina/química , Citoesqueleto de Actina/metabolismo , Bicamadas Lipídicas/química , Bicamadas Lipídicas/metabolismo , Actinas/química , Células Artificiais , Membrana Celular/química , Membrana Celular/metabolismo , Fenômenos Químicos , Biologia Computacional , Simulação por Computador , Citoesqueleto/química , Citoesqueleto/metabolismo , Íons/química , Íons/metabolismo , Modelos Moleculares , Simulação de Dinâmica Molecular , Ligação Proteica , Conformação Proteica , Eletricidade Estática
8.
Biosensors (Basel) ; 10(3)2020 Feb 29.
Artigo em Inglês | MEDLINE | ID: mdl-32121452

RESUMO

Surgical site infection represents a large burden of care in the National Health Service. Current methods for diagnosis include a subjective clinical assessment and wound swab culture that may take several days to return a result. Both techniques are potentially unreliable and result in delays in using targeted antibiotics. Volatile organic compounds (VOCs) are produced by micro-organisms such as those present in an infected wound. This study describes the use of a device to differentiate VOCs produced by an infected wound vs. colonised wound. Malodourous wound dressings were collected from patients, these were a mix of post-operative wounds and vascular leg ulcers. Wound microbiology swabs were taken and antibiotics commenced as clinically appropriate. A control group of soiled, but not malodorous wound dressings were collected from patients who had a split skin graft (SSG) donor site. The analyser used was a G.A.S. GC-IMS. The results from the samples had a sensitivity of 100% and a specificity of 88%, with a positive predictive value of 90%. An area under the curve (AUC) of 91% demonstrates an excellent ability to discriminate those with an infected wound from those without. VOC detection using GC-IMS has the potential to serve as a diagnostic tool for the differentiation of infected and non-infected wounds and facilitate the treatment of wound infections that is cost effective, non-invasive, acceptable to patients, portable, and reliable.


Assuntos
Análise Química do Sangue/métodos , Íons/metabolismo , Infecção dos Ferimentos/diagnóstico , Humanos
9.
Chemosphere ; 247: 125942, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32069721

RESUMO

We have evaluated the interactive toxicity of Cu(II) and Cd(II) in water with different hardness levels using adult zebrafish (Danio rerio). Zebrafish were exposed to Cd(II) (0.2-22 µM) or Cu(II) (0.1-8 µM) in single or binary exposures in very soft, moderately hard or very hard water. The whole body burdens of Cd(II) and Cu(II) reflect the net effect of biouptake and elimination, mortality was the indicator of toxicity, and whole body major ion content was measured to assess ion regulatory functions. Cu(II) was found to be more toxic than Cd(II) for zebrafish, and Cu(II) and Cd(II) exhibited a significant synergistic effect. The toxicity of metal ions increased upon decreasing the ionic strength of the exposure medium, probably due to elevated competition between metal ions with other cations in hard water and increased activity of Ca2+ pathways in soft water treatments. Whole body metal accumulation and the accumulation rate of both Cu and Cd increased as the metal ion concentration in the exposure medium increased. Nevertheless, neither parameter explained the observed synergistic effect on mortality. Finally, we observed a significant loss of whole body Na+ in fish which died during the metal exposure compared to surviving fish, irrespective of exposure conditions. Such an effect was not observed for other major cations (K+, Ca2+ and Mg2+). This observation suggests that, under the applied exposure conditions, survival was correlated to the capacity of the organism to maintain Na+ homeostasis.


Assuntos
Cádmio/toxicidade , Poluentes Químicos da Água/toxicidade , Peixe-Zebra/fisiologia , Animais , Cobre/toxicidade , Dureza , Íons/metabolismo , Metais/metabolismo , Sódio/metabolismo , Peixe-Zebra/metabolismo
10.
J Fish Biol ; 96(4): 986-1003, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32060920

RESUMO

The Mekong Delta is host to a large number of freshwater species, including a unique group of facultative air-breathing Anabantiforms. Of these, the striped snakehead (Channa striata), the climbing perch (Anabas testudineus), the giant gourami (Osphronemus goramy) and the snakeskin gourami (Trichogaster pectoralis) are major contributors to aquaculture production in Vietnam. The gastrointestinal responses to feeding in these four species are detailed here. Relative intestinal length was lowest in the snakehead, indicating carnivory, and 5.5-fold greater in the snakeskin, indicating herbivory; climbing perch and giant gourami were intermediate, indicating omnivory. N-waste excretion (ammonia-N + urea-N) was greatest in the carnivorous snakehead and least in the herbivorous snakeskin, whereas the opposite trend was observed for net K+ excretion. Similarly, the more carnivorous species had a greater stomach acidity than the more herbivorous species. Measurements of acid-base flux to water indicated that the greatest postprandial alkaline tide occurred in the snakehead and a potential acidic tide in the snakeskin. Additional findings of interest were high levels of both PCO2 (up to 40 mmHg) and HCO3 - (up to 33 mM) in the intestinal chyme of all four of these air-breathing species. Using in vitro gut sac preparations of the climbing perch, it was shown that the intestinal net absorption of fluid, Na+ and HCO3 - was upregulated by feeding but not net Cl- uptake, glucose uptake or K+ secretion. Upregulated net absorption of HCO3 - suggests that the high chyme (HCO3 - ) does not result from secretion by the intestinal epithelium. The possibility of ventilatory control of PCO2 to regulate postprandial acid-base balance in these air-breathing fish is discussed.


Assuntos
Comportamento Alimentar/fisiologia , Peixes/fisiologia , Trato Gastrointestinal/fisiologia , Amônia/metabolismo , Animais , Água Doce , Mucosa Intestinal/metabolismo , Íons/metabolismo , Período Pós-Prandial , Sódio/metabolismo , Ureia/metabolismo , Vietnã
11.
Ecotoxicol Environ Saf ; 193: 110345, 2020 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-32092578

RESUMO

Many areas of the world are affected simultaneously by salinity and heavy metal pollution. Halophytes are considered as useful candidates in remediation of such soils due to their ability to withstand both osmotic stress and ion toxicity deriving from high salt concentrations. Quinoa (Chenopodium quinoa Willd) is a halophyte with a high resistance to abiotic stresses (drought, salinity, frost), but its capacity to cope with heavy metals has not yet been fully investigated. In this pot experiment, we investigated phytoextraction capacity, effects on nutrient levels (P and Fe), and changes in gene expression in response to application of Cr(III) in quinoa plants grown on saline or non-saline soil. Plants were exposed for three weeks to 500 mg kg-1 soil of Cr(NO3)3·9H2O either in the presence or absence of 150 mM NaCl. Results show that plants were able tolerate this soil concentration of Cr(III); the metal was mainly accumulated in roots where it reached the highest concentration (ca. 2.6 mg g-1 DW) in the presence of NaCl. On saline soil, foliar Na concentration was significantly reduced by Cr(III). Phosphorus translocation to leaves was reduced in the presence of Cr(III), while Fe accumulation was enhanced by treatment with NaCl alone. A real-time RT-qPCR analysis was conducted on genes encoding for sulfate, iron, and phosphate transporters, a phytochelatin, a metallothionein, glutathione synthetase, a dehydrin, Hsp70, and enzymes responsible for the biosynthesis of proline (P5CS), glycine betaine (BADH), tocopherols (TAT), and phenolic compounds (PAL). Cr(III), and especially Cr(III)+NaCl, affected transcript levels of most of the investigated genes, indicating that tolerance to Cr is associated with changes in phosphorus and sulfur allocation, and activation of stress-protective molecules. Moderately saline conditions, in most cases, enhanced this response, suggesting that the halophytism of quinoa could contribute to prime the plants to respond to chromium stress.


Assuntos
Chenopodium quinoa/efeitos dos fármacos , Chenopodium quinoa/metabolismo , Cromo/toxicidade , Salinidade , Poluentes do Solo/toxicidade , Biodegradação Ambiental , Transporte Biológico/efeitos dos fármacos , Chenopodium quinoa/genética , Cromo/farmacocinética , Expressão Gênica/efeitos dos fármacos , Íons/metabolismo , Ferro/metabolismo , Chumbo/metabolismo , Folhas de Planta/metabolismo , Raízes de Plantas/metabolismo , Prolina/biossíntese , Plantas Tolerantes a Sal/efeitos dos fármacos , Plantas Tolerantes a Sal/genética , Plantas Tolerantes a Sal/metabolismo , Sódio/metabolismo , Cloreto de Sódio/farmacologia , Poluentes do Solo/farmacocinética , Estresse Fisiológico , Enxofre/metabolismo , Tocoferóis/metabolismo
12.
Protein Expr Purif ; 169: 105586, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32001358

RESUMO

Eukaryotic recombinant proteins expressed in bacterial cells usually aggregate within the cells as inclusion bodies. Despite the widely-accepted theory considering inclusion bodies as inactive materials, inclusion bodies may contain large amounts of correctly-folded active recombinant proteins. Proteins trapped in inclusion bodies can be released using a high pH solution (pH ≥ 11); however, they may undergo structural changes in such pH conditions that may lead to their inactivation. Shifting in pH alongside the use of metal ions can help recover protein activity. The model protein we used in this study, 9R-Nimo.scFv, is highly active when extracted from bacterial inclusion bodies at high pH condition (pH 12) but loses its activity when pH is reduced to pH 7. We evaluated the capacity of nine salt solutions in terms of recovering protein activity in neutral pH conditions and found that ZnSO4 solution was the best one for this purpose. KNO3 and MnSO4 were also found to have a good capacity for recovering protein activity, as well.


Assuntos
Corpos de Inclusão/química , Íons/análise , Proteínas Recombinantes/química , Clonagem Molecular/métodos , Escherichia coli/metabolismo , Concentração de Íons de Hidrogênio , Íons/metabolismo , Agregados Proteicos , Dobramento de Proteína , Proteínas Recombinantes/biossíntese
13.
Chem Asian J ; 15(7): 986-994, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-32017445

RESUMO

Many biomolecules exist as internal ion pairs or zwitterions within a biologically relevant pH range. Despite their importance, the molecular recognition of this type of systems is specially challenging due to their strong solvation in aqueous media, and their trend to form folded or self-assembled structures by pairing of charges of different sign. In this Minireview, we will discuss the molecular recognition of zwitterions using non-natural, synthetic receptors. This contribution does not intend to make a full in-depth revision of the existing research in the field, but a personal overview with selected representative examples from the recent literature.


Assuntos
Íons/metabolismo , Receptores Artificiais/metabolismo , Sistemas de Liberação de Medicamentos/métodos , Ligação de Hidrogênio , Concentração de Íons de Hidrogênio , Conformação Molecular , Solubilidade
14.
Adv Immunol ; 145: 187-241, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32081198

RESUMO

Metals are essential components in all forms of life required for the function of nearly half of all enzymes and are critically involved in virtually all fundamental biological processes. Especially, the transition metals iron (Fe), zinc (Zn), manganese (Mn), nickel (Ni), copper (Cu) and cobalt (Co) are crucial micronutrients known to play vital roles in metabolism as well due to their unique redox properties. Metals carry out three major functions within metalloproteins: to provide structural support, to serve as enzymatic cofactors, and to mediate electron transportation. Metal ions are also involved in the immune system from metal allergies to nutritional immunity. Within the past decade, much attention has been drawn to the roles of metal ions in the immune system, since increasing evidence has mounted to suggest that metals are critically implicated in regulating both the innate immune sensing of and the host defense against invading pathogens. The importance of ions in immunity is also evidenced by the identification of various immunodeficiencies in patients with mutations in ion channels and transporters. In addition, cancer immunotherapy has recently been conclusively demonstrated to be effective and important for future tumor treatment, although only a small percentage of cancer patients respond to immunotherapy because of inadequate immune activation. Importantly, metal ion-activated immunotherapy is becoming an effective and potential way in tumor therapy for better clinical application. Nevertheless, we are still in a primary stage of discovering the diverse immunological functions of ions and mechanistically understanding the roles of these ions in immune regulation. This review summarizes recent advances in the understanding of metal-controlled immunity. Particular emphasis is put on the mechanisms of innate immune stimulation and T cell activation by the essential metal ions like calcium (Ca2+), zinc (Zn2+), manganese (Mn2+), iron (Fe2+/Fe3+), and potassium (K+), followed by a few unessential metals, in order to draw a general diagram of metalloimmunology.


Assuntos
Imunidade Inata , Metais/metabolismo , Transdução de Sinais/imunologia , Animais , Cálcio/química , Cálcio/metabolismo , Cálcio/fisiologia , Enzimas , Humanos , Imunoterapia , Íons/química , Íons/metabolismo , Ferro/metabolismo , Ferro/fisiologia , Manganês/metabolismo , Manganês/fisiologia , Metais/química , Neoplasias/tratamento farmacológico , Neoplasias/enzimologia , Neoplasias/imunologia , Potássio/química , Potássio/metabolismo , Potássio/fisiologia , Zinco/química , Zinco/deficiência , Zinco/fisiologia
15.
Int J Mol Sci ; 21(2)2020 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-31947679

RESUMO

Two-pore domain potassium (K2P) channels maintain the cell's background conductance by stabilizing the resting membrane potential. They assemble as dimers possessing four transmembrane helices in each subunit. K2P channels were crystallized in "up" and "down" states. The movements of the pore-lining transmembrane TM4 helix produce the aperture or closure of side fenestrations that connect the lipid membrane with the central cavity. When the TM4 helix is in the up-state, the fenestrations are closed, while they are open in the down-state. It is thought that the fenestration states are related to the activity of K2P channels and the opening of the channels preferentially occurs from the up-state. TASK-2, a member of the TALK subfamily of K2P channels, is opened by intracellular alkalization leading the deprotonation of the K245 residue at the end of the TM4 helix. This charge neutralization of K245 could be sensitive or coupled to the fenestration state. Here, we describe the relationship between the states of the intramembrane fenestrations and K245 residue in TASK-2 channel. By using molecular modeling and simulations, we show that the protonated state of K245 (K245+) favors the open fenestration state and, symmetrically, that the open fenestration state favors the protonated state of the lysine residue. We show that the channel can be completely blocked by Prozac, which is known to induce fenestration opening in TREK-2. K245 protonation and fenestration aperture have an additive effect on the conductance of the channel. The opening of the fenestrations with K245+ increases the entrance of lipids into the selectivity filter, blocking the channel. At the same time, the protonation of K245 introduces electrostatic potential energy barriers to ion entrance. We computed the free energy profiles of ion penetration into the channel in different fenestration and K245 protonation states, to show that the effects of the two transformations are summed up, leading to maximum channel blocking. Estimated rates of ion transport are in qualitative agreement with experimental results and support the hypothesis that the most important barrier for ion transport under K245+ and open fenestration conditions is the entrance of the ions into the channel.


Assuntos
Concentração de Íons de Hidrogênio , Canais de Potássio de Domínios Poros em Tandem/química , Canais de Potássio de Domínios Poros em Tandem/metabolismo , Sequência de Aminoácidos , Sítios de Ligação , Células HEK293 , Humanos , Ativação do Canal Iônico , Íons/química , Íons/metabolismo , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Ligação Proteica , Conformação Proteica , Relação Estrutura-Atividade
16.
J Chem Theory Comput ; 16(1): 700-710, 2020 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-31769987

RESUMO

Two permeation mechanisms, namely the water-chain-assisted mechanism and the dehydration mechanism, have been proposed for ions through lipid membranes. In previous studies, multiple reaction coordinates and potential of mean force calculations have been applied in studying such complex transmembrane processes of ions. To reduce the expensive computational cost, we develop two new reaction coordinates in our recent work and in this work to study the two permeation mechanisms. An intrinsically one-dimensional free energy calculation method developed in our recent work is successfully employed in these studies: First, one-dimensional umbrella samplings are performed using the two reaction coordinates. Then, bin segmentations are performed along the transition paths in multidimensional phase spaces. Finally, the weighted least-square analysis method (Welsam) is used for free energy analysis. Based on the new reaction coordinates and the one-dimensional free energy calculation method, we systematically study the two transmembrane permeation mechanisms of sodium ion and chloride ion through lipid bilayers with different thicknesses. Our results suggest that the water-chain-assisted mechanism is dominant for cations, whereas the dehydration mechanism is competitive for anions through thick membranes, which is consistent with previous experimental results.


Assuntos
Íons/metabolismo , Bicamadas Lipídicas/metabolismo , Termodinâmica , Água/metabolismo , Algoritmos , Permeabilidade da Membrana Celular , Simulação por Computador , Transporte de Íons , Modelos Biológicos , Modelos Moleculares
17.
J Environ Sci Health B ; 55(2): 166-173, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31588841

RESUMO

Toxicity of heavy metals to living organisms is a worldwide research topic. Although, much has been discovered about cadmium and nickel impact on biological systems, a lot still remains unclear. We used inductively coupled plasma - optical emission spectroscopy to address the question of the effect of two different heavy metals nickel, and cadmium on intracellular ion balance. Increase or decrease of the content of several essential cations including Ca2+, Na+, K+, Mg2+, Cu2+, Fe3+ in the yeast Schizosaccharomyces pombe was determined. Our results revealed that the cell exposure to high nickel and cadmium concentrations led to significant elevation of Ca2+, Na+, Mg2+, Cu2+, Fe3+ levels in the yeast cell, while the content of K+ decreased. Correlation analyses showing in the presence of nickel and cadmium strong positive correlation among each tested element (Ca2+, Na+, Cu2+, Mg2+ and Fe3+) except for K+, demonstrate the significant impact of heavy metal treatment to ion homeostasis of the cell. Our data indicate that acute nickel and cadmium contamination leads to substantial ionome misbalance in yeast.


Assuntos
Cádmio/toxicidade , Metais/metabolismo , Níquel/toxicidade , Schizosaccharomyces/efeitos dos fármacos , Schizosaccharomyces/metabolismo , Relação Dose-Resposta a Droga , Homeostase/efeitos dos fármacos , Íons/metabolismo , Schizosaccharomyces/crescimento & desenvolvimento
18.
Ecotoxicol Environ Saf ; 188: 109894, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31706239

RESUMO

Modulation of plant salt tolerance has been drawing great attention. Thymol is a kind of natural chemical that has been developed as anti-microbial reagent and medicine. To date, we still have limited knowledge about thymol-modulated plant physiology. In this work, physiological, histochemical, and biochemical methods were adopted to study thymol-conferred salt resistance in the root of rice (Oryza sativa). Thymol significantly rescued root growth under salt stress. Thymol ameliorated cell membrane damage, oxidative stress, ROS accumulation, and cell death in roots under salt stress. Thymol-attenuated oxidative stress may be resulted from the activation of anti-oxidative capacity, including both enzymatic and non-enzymatic system. Thymol treatment significantly decreased Na+ content in root cells upon salt stress, which might be ascribed to the upregulation of OsSOS1 (salt overly sensitive 1) facilitating Na+ exclusion. In addition, thymol stimulated the expression of genes encoding tonoplast OsNHX (Na+/H+antiporter), which may help root cells to compartmentalize Na+ in vacuole. The results of these works evidenced that thymol was capable of inducing salt tolerance by reestablishing ROS homeostasis and modulating cellular Na+ flux in rice roots. These findings may be applicable to improve crop growth in salinity area.


Assuntos
Antioxidantes/metabolismo , Homeostase/efeitos dos fármacos , Oryza/efeitos dos fármacos , Tolerância ao Sal/efeitos dos fármacos , Sódio/metabolismo , Timol/farmacologia , Íons/metabolismo , Oryza/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Proteínas de Plantas/metabolismo , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/metabolismo , Plantas Tolerantes a Sal , Trocadores de Sódio-Hidrogênio/metabolismo
19.
Biochemistry ; 59(4): 520-529, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-31887021

RESUMO

Krokinobacter rhodopsin 2 (KR2) serves as a light-driven sodium ion pump in the presence of sodium ion and works as a proton pump in the presence of larger monovalent cations such as potassium ion, rubidium ion, and cesium ion. Recent crystallographic studies revealed that KR2 forms a pentamer and possesses an ion binding site at the subunit interface. It is assumed that sodium ion bound at this binding site is not transported but contributes to the thermal stability. Because KR2 can convert its function in response to coexisting cation species, this ion binding site is likely to be involved in ion transport selectively. However, how sodium ion binding affects the structure of the retinal chromophore, which plays a crucial role in ion transport, remains poorly understood. Here, we observed the structure of the retinal chromophore under a wide range of cation concentrations using visible absorption and resonance Raman spectroscopy. We discovered that the hydrogen bond formed between the Schiff base of the retinal chromophore and its counterion, Asp116, is weakened upon binding of sodium ion. This allosteric communication between the Schiff base and the ion binding site at the subunit interface likely increases the apparent efficiency of sodium ion transport. In addition, this study demonstrates the significance of sodium ion binding: even though sodium ion is not transported, binding regulates the structure around the Schiff base and stabilizes the oligomeric structure.


Assuntos
Bombas de Próton/química , Rodopsina/química , Rodopsina/metabolismo , Sítios de Ligação , Flavobacteriaceae/enzimologia , Flavobacteriaceae/metabolismo , Ligação de Hidrogênio , Transporte de Íons/fisiologia , Íons/metabolismo , Potássio/metabolismo , Bombas de Próton/metabolismo , Retina/metabolismo , Sódio/metabolismo , ATPase Trocadora de Sódio-Potássio/metabolismo
20.
J Chromatogr B Analyt Technol Biomed Life Sci ; 1134-1135: 121857, 2019 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-31790918

RESUMO

In this study, the ionic profile and pH of exhaled breath condensate (EBC) in a group of patients with acid and weakly acid reflux and no-reflux controls were compared. A portable sampler was used for non-invasive EBC collection from five exhalations. The ionic profile (anions, cations, organic acids) and pH of the collected EBC samples were measured by capillary electrophoresis with contactless conductivity detection and a pH microelectrode, respectively. Several ions were elevated in the patient groups. Sodium cation was elevated in weakly acid reflux (significance level p < 0.01) and acid reflux (p < 0.05) compared to no-reflux controls. Butyrate and propionate were elevated in both acid reflux and weakly acid reflux compared to no-reflux controls (butyrate: p < 0.01, propionate: p < 0.05). The median values of pH (after de-aeration with N2) were also significantly higher (p < 0.01) in groups with acid reflux and weakly acid reflux than in the control group with no reflux. The ionic analysis and simultaneous pH measurement offer a simple, cheap, fast, and non-invasive approach in gastroesophageal reflux disease diagnostics.


Assuntos
Testes Respiratórios/métodos , Eletroforese Capilar/métodos , Refluxo Gastroesofágico/diagnóstico , Refluxo Gastroesofágico/metabolismo , Íons/análise , Adulto , Idoso , Butiratos/análise , Feminino , Humanos , Concentração de Íons de Hidrogênio , Íons/metabolismo , Masculino , Pessoa de Meia-Idade , Propionatos/análise , Sódio/análise
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