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1.
Plant Cell ; 36(4): 1159-1181, 2024 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-38134410

RESUMO

Plants have unique responses to fluctuating light conditions. One such response involves chloroplast photorelocation movement, which optimizes photosynthesis under weak light by the accumulation of chloroplasts along the periclinal side of the cell, which prevents photodamage under strong light by avoiding chloroplast positioning toward the anticlinal side of the cell. This light-responsive chloroplast movement relies on the reorganization of chloroplast actin (cp-actin) filaments. Previous studies have suggested that CHLOROPLAST UNUSUAL POSITIONING 1 (CHUP1) is essential for chloroplast photorelocation movement as a regulator of cp-actin filaments. In this study, we conducted comprehensive analyses to understand CHUP1 function. Functional, fluorescently tagged CHUP1 colocalized with and was coordinately reorganized with cp-actin filaments on the chloroplast outer envelope during chloroplast movement in Arabidopsis thaliana. CHUP1 distribution was reversibly regulated in a blue light- and phototropin-dependent manner. X-ray crystallography revealed that the CHUP1-C-terminal domain shares structural homology with the formin homology 2 (FH2) domain, despite lacking sequence similarity. Furthermore, the CHUP1-C-terminal domain promoted actin polymerization in the presence of profilin in vitro. Taken together, our findings indicate that CHUP1 is a plant-specific actin polymerization factor that has convergently evolved to assemble cp-actin filaments and enables chloroplast photorelocation movement.


Assuntos
Proteínas de Arabidopsis , Arabidopsis , Actinas , Proteínas de Arabidopsis/genética , Polimerização , Proteínas de Cloroplastos/genética , Arabidopsis/genética , Citoesqueleto de Actina , Cloroplastos/fisiologia , Luz , Movimento
2.
Psychol Health Med ; 27(9): 2021-2029, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-34779312

RESUMO

This study examined whether perceiving an event as a trauma influenced a cognitive processing model explaining posttraumatic growth (PTG). A cross-sectional questionnaire survey was conducted with 311 university students from eight universities in Japan. The participants provided information about the most stressful event they had experienced and completed the expanded version of the PTG Inventory, Core Belief Inventory, Event Related Rumination Inventory, and Cognitive and Emotional Processing from Disclosure Inventory. A multi-group structural equation modeling was conducted by dividing the participants into two groups depending on whether they identified the most stressful event as a trauma. The model with no constraint showed a good fit. The model with partial constraint showed a better fit than the models with no constraint or full constraint. The difference of the model was seen as a covariance between the Event Related Rumination Inventory and the Cognitive and Emotional Processing from Disclosure Inventory. The results demonstrated configural invariance and partial metric invariance. This indicated that PTG would be recognized irrespective of whether the event was perceived as a trauma. This study also indicated that different factors out of the model could be associated with the ruminative process and disclosure process. The importance of focusing on the process of PTG, regardless of an individual's perception of the event, was emphasized, especially for factors related to rumination and disclosure.


Assuntos
Crescimento Psicológico Pós-Traumático , Transtornos de Estresse Pós-Traumáticos , Adaptação Psicológica , Cognição , Estudos Transversais , Humanos , Transtornos de Estresse Pós-Traumáticos/psicologia , Estudantes/psicologia , Universidades
3.
Sensors (Basel) ; 21(3)2021 Jan 26.
Artigo em Inglês | MEDLINE | ID: mdl-33530394

RESUMO

Asthma and chronic obstructive pulmonary disease are associated with nocturnal cough and changes in heart rate. In this work, the authors propose a proof-of-concept non-contact system for performing capacitive electrocardiogram (cECG) and cough-associated capacitive electromyogram (cEMG) measurements using cloth electrodes under a pillowcase. Two electrodes were located along with the approximate vector of lead II ECG and were used for both cECG and cEMG measurements. A signature voltage follower was introduced after each electrode to detect biopotentials with amplitudes of approximately 100 µV. A bootstrapping technique and nonlinear electrical component were combined and implemented in the voltage follower to attain a high input impedance and rapid static discharge. The measurement system was evaluated in a laboratory experiment for seven adult males and one female (average age: 22.5 ± 1.3 yr). The accuracy of R-wave detection for 2-min resting periods was 100% in six subjects, with an overall average of 87.5% ± 30.0%. Clearly visible cEMGs were obtained for each cough motion for all subjects, synchronized with reference EMGs from submental muscle. Although there remains room for improvement in practical use, the proposed system is promising for unobtrusive detection of heart rate and cough over a prolonged period of time.


Assuntos
Tosse , Eletrocardiografia , Adulto , Tosse/diagnóstico , Eletrodos , Eletromiografia , Feminino , Frequência Cardíaca , Humanos , Masculino , Adulto Jovem
4.
Microbiology (Reading) ; 163(7): 1071-1080, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28691662

RESUMO

The Rcs phosphorelay signal transduction system of Escherichia coli controls genes for capsule production and many other envelope-related functions and is implicated in biofilm formation. The outer-membrane lipoprotein RcsF is an essential component of the Rcs system. Mislocalization of RcsF to the periplasm or the cytoplasmic membrane leads to high activation of the Rcs system, suggesting that RcsF functions by interacting with the cytoplasmic membrane component(s) of the system in activating the system. This is consistent with the result reported by Cho et al. (Cell159, 1652-1664, 2014) showing that RcsF interacts with the periplasmic domain (YrfFperi) of the inner-membrane protein YrfF (IgaA in Salmonella enterica serovar Typhimurium), which is a negative regulator of the Rcs system. In this study we show that RcsF also interacts with the periplasmic domain of the innermembrane-localized histidine kinase RcsC (RcsCperi). RcsCperi, which was secreted to the periplasm by fusion to maltose-binding protein, titrated RcsF's activating effect. A bimolecular fluorescence complementation experiment showed interaction of RcsF with RcsCperi, as well as with YrfFperi. We conclude that RcsF interacts with the periplasmically exposed region of RcsC, as well as with that of YrfF.


Assuntos
Proteínas de Escherichia coli/metabolismo , Escherichia coli/metabolismo , Histidina Quinase/metabolismo , Lipoproteínas/metabolismo , Complexos Multienzimáticos/metabolismo , Fosfoproteínas Fosfatases/metabolismo , Proteínas Quinases/metabolismo , Transdução de Sinais , Escherichia coli/enzimologia , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Regulação Bacteriana da Expressão Gênica , Histidina Quinase/genética , Lipoproteínas/genética , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Complexos Multienzimáticos/genética , Fosfoproteínas Fosfatases/genética , Ligação Proteica , Proteínas Quinases/genética
5.
Asian J Psychiatr ; 81: 103462, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36641967

RESUMO

Suicides by university students in Japan have increased with the onset of the COVID- 19 pandemic. Changes in the suicidality of clients in student counseling centers are unknown. We compared OQ 45.2, suicidal risk, and suicidality before and after the pandemic, testing 1801 clients at the Student Counseling Center of University A in Japan. The post-group exhibited significantly decreases in all suicide-related indices. Results reveal that fewer students may feel suicidal and that the number of consultations with suicidal students may have decreased. It is important to build support systems easier for students to access in crises and alone.


Assuntos
COVID-19 , Suicídio , Humanos , Suicídio/psicologia , Universidades , População do Leste Asiático , Aconselhamento , Ideação Suicida , Estudantes/psicologia
6.
ACS Appl Mater Interfaces ; 15(29): 34809-34817, 2023 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-37435978

RESUMO

The development of efficient and stable oxygen-reducing electrodes is challenging but vital for the production of efficient electrochemical cells. Composite electrodes composed of mixed ionic-electronic conducting La1-xSrxCo1-yFeyO3-δ and ionic conducting doped CeO2 are considered promising components for solid oxide fuel cells. However, no consensus has been reached regarding the reasons of the good electrode performance, and inconsistent performance has been reported among various research groups. To mitigate the difficulties related to analyzing composite electrodes, this study applied three-terminal cathodic polarization to dense and nanoscale La0.6Sr0.4CoO3-δ-Ce0.8Sm0.2O1.9 (LSC-SDC) model electrodes. The critical factors determining the performance of the composite electrodes are the segregation of catalytic cobalt oxides to the electrolyte interfaces and the oxide-ion conducting paths provided by SDC. The addition of Co3O4 to the LSC-SDC electrode resulted in reduced LSC decomposition; thus, the interfacial and electrode resistances were low and stable. In the Co3O4-added LSC-SDC electrode under cathodic polarization, Co3O4 turned wurtzite-type CoO, which suggested that the Co3O4 addition suppressed the decomposition of LSC and, thus, the cathodic bias was maintained from the electrode surface to electrode-electrolyte interface. This study shows that cobalt oxide segregation behavior must be considered when discussing the performance of composite electrodes. Furthermore, by controlling the segregation process, microstructure, and phase evolution, stable low-resistance composite oxygen-reducing electrodes can be fabricated.

7.
Biosci Biotechnol Biochem ; 76(8): 1511-7, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22878195

RESUMO

In Japan, kudzu is a familiar plant, well-known as an ingredient in the Japanese-style confections kudzu-kiri and kudzu-mochi. In this study, we focused on the flower of kudzu (Pueraria thomsonii) and conducted a clinical trial to investigate the effects of Pueraria thomsonii flower extract (PFE) on obesity using obese Japanese males and females (BMI ≥ 25 kg/m(2)). Eighty-one obese subjects were randomly divided into three groups and consumed test food containing 300 mg of PFE, 200 mg of PFE, and a placebo over 12 weeks. The results indicate that PFE intake reduces BMI and decreases, the visceral fat area, but not the subcutaneous fat area. In addition, the decrease in visceral fat area showed no sexual dimorphism. Consequently, we propose that PFE intake expresses its BMI reduction effects via a decrease in visceral fat area.


Assuntos
Flores/química , Gordura Intra-Abdominal/efeitos dos fármacos , Obesidade/tratamento farmacológico , Extratos Vegetais/farmacologia , Pueraria/química , Adulto , Idoso , Povo Asiático , Composição Corporal/efeitos dos fármacos , Índice de Massa Corporal , Feminino , Humanos , Gordura Intra-Abdominal/patologia , Masculino , Pessoa de Meia-Idade , Obesidade/patologia , Placebos , Gordura Subcutânea/efeitos dos fármacos , Gordura Subcutânea/patologia , Triglicerídeos/sangue
8.
Biochemistry ; 49(26): 5445-54, 2010 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-20518513

RESUMO

Herbicides targeting photosystem II (PSII) block the electron transfer beyond Q(A) by binding to the Q(B) site. Upon binding, the redox potential of Q(A) shifts differently depending on the types of herbicides. In this study, we have investigated the structures, interactions, and locations of phenolic herbicides in the Q(B) site to clarify the molecular mechanism of the Q(A) potential shifts by herbicides. Fourier transform infrared (FTIR) difference spectra upon photoreduction of the preoxidized non-heme iron (Fe(2+)/Fe(3+) difference) were measured with PSII membranes in the presence of bromoxynil or ioxynil. The CN and CO stretching vibrations of these phenolic herbicides were identified at 2215-2200 and 1516-1505 cm(-1), respectively, in the Fe(2+)/Fe(3+) difference spectra. Comparison with the spectra of bromoxynil in ethanol solutions along with density functional theory analysis strongly suggests that the phenolic herbicides take a deprotonated form in the binding pocket. In addition, the CN stretching, NH bending, and NH stretching vibrations of a His side chain, which were found at 1109-1101, 1187-1185, and 3000-2500 cm(-1), respectively, in the Fe(2+)/Fe(3+) difference spectra, showed characteristic features in the presence of phenolic herbicides. These signals are probably attributed to D1-His215, one of the ligands to the non-heme iron. Docking calculations for herbicides to the Q(B) pocket confirmed the binding of deprotonated bromoxynil to D1-His215 at the CO group, whereas the protonated form of bromoxynil and DCMU were found to bind to the opposite side of the pocket without an interaction with D1-His215. From these results, it is proposed that a strong hydrogen bond of the phenolate CO group with D1-His215 induces the change in the hydrogen bond strength of the Q(A) CO group through the Q(A)-His-Fe-His-phenolate bridge causing the downshift of the Q(A) redox potential.


Assuntos
Herbicidas/química , Ligação de Hidrogênio , Complexo de Proteína do Fotossistema II/química , Sítios de Ligação , Estrutura Molecular , Oxirredução , Fenóis/química , Complexo de Proteína do Fotossistema II/metabolismo , Proteínas de Plantas/química , Proteínas de Plantas/metabolismo , Ligação Proteica , Spinacia oleracea/química , Spinacia oleracea/metabolismo
9.
Plant Cell Physiol ; 51(8): 1372-6, 2010 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-20562448

RESUMO

An auxilin-like J-domain-containing protein, JAC1, is necessary for chloroplast movement in Arabidopsis thaliana, to capture photosynthetic light efficiently under weak light conditions. Here, we performed crystallographic and functional analyses of the J-domain of JAC1. The crystal structure of the J-domain is quite similar to that of bovine auxilin, and possesses a similar positively charged surface, which probably forms the interface with the Hsp70 chaperone. The mutation of the highly conserved HPD motif of the JAC1 J-domain abrogated the chloroplast photorelocation response. These results suggest that the requirement of JAC1 in chloroplast photorelocation movement is attributable to the J-domain's cochaperone activity.


Assuntos
Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Auxilinas/metabolismo , Cloroplastos/fisiologia , Sequência de Aminoácidos , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Auxilinas/genética , Regulação da Expressão Gênica de Plantas , Modelos Moleculares , Dados de Sequência Molecular , Mutação , Domínios e Motivos de Interação entre Proteínas , Estrutura Terciária de Proteína , Alinhamento de Sequência
10.
Asian J Psychiatr ; 47: 101831, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31677397

RESUMO

This study investigated young Japanese adults' attitudes toward suicide and factors affecting them. Results revealed that 28.78% of respondents had serious suicidal ideation history; 18.53% knew suicidal others; and 15.29% took suicide-prevention training. A t-test showed that respondents' "Right to suicide" and "Common occurrence" scores were higher with suicidal ideation history, but "Unjustified behavior" was lower than in those without history. Results indicated that certain young adults were unsupportive by being permissive of suicide due to their suicidal ideation or becoming bystanders due to inexperience. For young Japanese adults, enhancing preventive education to alter permissive/bystander attitudes is crucial.


Assuntos
Atitude Frente a Morte/etnologia , Conhecimentos, Atitudes e Prática em Saúde/etnologia , Suicídio/etnologia , Adolescente , Adulto , Feminino , Humanos , Japão/etnologia , Masculino , Ideação Suicida , Adulto Jovem
11.
Microscopy (Oxf) ; 69(5): 298-303, 2020 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-32453415

RESUMO

A scanning electron microscope transition edge sensor has been developed to analyze the minor or trace constituents contained in a bulk sample and small particles on the sample under a low accelerating voltage (typically <3 keV). The low accelerating voltage enables to improve the spatial analysis resolution because the primary electron diffusion length is limited around the sample surface. The characteristic points of our transition edge sensor are 1) high-energy resolution at 7.2 eV@Al-Kα, 2) continuous operation by using a cryogen-free dilution refrigerator and 3) improvement of transmission efficiency at B-Kα by using thin X-ray film windows between the sample and detector (about 30 times better than our previous system). Our system could achieve a stabilization of the peak shift at Nd-Mα (978 eV) within 1 eV during an operation time of 27 000 s. The detection limits with B-Kα for detection times 600 and 27 000 s were 0.27 and 0.038 wt%, respectively. We investigated the peak separation ability by measuring the peak intensity ratio between the major constitute (silicon) and the minor constitute (tungsten) because the Si-Kα line differs from the W-Mα line by only 35 eV and a small W-Mα peak superimposed on the tail of the large Si-Kα peak. The peak intensity ratio (I(W-Mα)/I(Si-Kα)) was adjusted by the W particle area ratio compared with the Si substrate area. The transition edge sensor could clearly separate the Si-Kα and W-Mα lines even under a peak intensity ratio of 0.01.

12.
Elife ; 42015 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-25853343

RESUMO

tRNAs are unique among various RNAs in that they shuttle between the nucleus and the cytoplasm, and their localization is regulated by nutrient conditions. Although nuclear export of tRNAs has been well documented, the import machinery is poorly understood. Here, we identified Ssa2p, a major cytoplasmic Hsp70 in Saccharomyces cerevisiae, as a tRNA-binding protein whose deletion compromises nuclear accumulation of tRNAs upon nutrient starvation. Ssa2p recognizes several structural features of tRNAs through its nucleotide-binding domain, but prefers loosely-folded tRNAs, suggesting that Ssa2p has a chaperone-like activity for RNAs. Ssa2p also binds Nup116, one of the yeast nucleoporins. Sis1p and Ydj1p, cytoplasmic co-chaperones for Ssa proteins, were also found to contribute to the tRNA import. These results unveil a novel function of the Ssa2p system as a tRNA carrier for nuclear import by a novel mode of substrate recognition. Such Ssa2p-mediated tRNA import likely contributes to quality control of cytosolic tRNAs.


Assuntos
Regulação Fúngica da Expressão Gênica , Proteínas de Choque Térmico HSP40/metabolismo , Proteínas de Choque Térmico HSP70/metabolismo , RNA de Transferência/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/metabolismo , Transporte Ativo do Núcleo Celular/genética , Sequência de Bases , Sítios de Ligação , Núcleo Celular/metabolismo , Citosol/metabolismo , Proteínas de Choque Térmico HSP40/genética , Proteínas de Choque Térmico HSP70/genética , Dados de Sequência Molecular , Complexo de Proteínas Formadoras de Poros Nucleares/genética , Complexo de Proteínas Formadoras de Poros Nucleares/metabolismo , Conformação de Ácido Nucleico , Fosforilação , Ligação Proteica , Transporte de RNA/genética , RNA de Transferência/genética , Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/genética , Transdução de Sinais
13.
Artigo em Inglês | MEDLINE | ID: mdl-25114709

RESUMO

Young barley leaf is consumed as a popular green-colored drink, which is named "Aojiru" in Japan. In the present study, we examined effects of young barley leaf powder (BL) on gastrointestinal transit time (GTT) and fecal moisture and weight in comparison with wheat bran (WB) in male Sprague-Dawley rats. In addition, an attempt was made to identify BL components responsible for these effects by using various fractions of BL. Additionally, we examined the water-holding capacity and setting volume of BL in vitro. We also examined the granular structures of BL with a scanning electron microscope. As a result, BL supplementation in the diet increased the fecal weight and shortened GTT. Our results demonstrate that the active component responsible for the effect on increasing the fecal volume in BL is the water-insoluble dietary fiber fraction and that this effect is thought to be caused by stimulation of the gut tract by the pH lowering. Furthermore, the high laxative action of BL was thought to be ascribable to the high water-holding capacity due to the complicated structures of BL.

14.
J Food Sci ; 78(11): T1814-21, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24245900

RESUMO

Kudzu has been widely used as an herbal medicine in China. The root of the kudzu is also well known as an antipyretic and analgesic in treatment of the common cold, while its flower has been used to treat alcohol intoxication, alcohol abuse, and dysentery. Pueraria flower extract (PFE) is a hot water extract derived from the flower of the kudzu, Pueraria thomsonii Benth. (Fabaceae), oral intake of which exhibits anti-obesity properties in mice and humans. In this study, we conducted acute and subchronic toxicity studies for an evaluation of safety. In the acute study, PFE (5 g/kg body weight) was orally administered to ddY mice. For 14 d after administration, no deaths or abnormal changes were observed in general signs, body weight (BW), or food consumption, and no abnormal findings were observed in the major organs and tissues of either males or females at necropsy. The oral LD50 of PFE was therefore estimated to be higher than 5 g/kg BW. In the subchronic study, PFE was mixed into the diet in place of powdered CRF-1 and administered at concentrations of 0% (control), 0.5%, 1.5%, and 5.0% to male and female Sprague-Dawley rats for 90 d. No mortality or toxicological changes were observed during the experimental period. Blood biochemical, hematological, and urinary parameters revealed no toxicologically significant changes. Furthermore, no anatomical or histopathological changes due to PFE were observed. The no-observed adverse-effect-level of PFE was thus estimated to be 5.0% in the diet (male: 3.0 g/kg BW/d; female: 3.5 g/kg BW/d).


Assuntos
Flores/química , Extratos Vegetais/toxicidade , Pueraria/química , Animais , Fármacos Antiobesidade/toxicidade , Peso Corporal , Feminino , Dose Letal Mediana , Masculino , Camundongos , Nível de Efeito Adverso não Observado , Plantas Medicinais/química , Ratos , Ratos Sprague-Dawley , Testes de Toxicidade Aguda , Testes de Toxicidade Subcrônica
15.
Artigo em Inglês | MEDLINE | ID: mdl-24348688

RESUMO

Barley (Hordeum vulgare L.) is a well-known cereal plant. Young barley leaf is consumed as a popular green-colored drink, which is named "Aojiru" in Japan. We examined the effects of barley leaf powder (BLP) and insoluble fibers derived from BLP on postprandial blood glucose in rats and healthy Japanese volunteers. BLP and insoluble fibers derived from BLP suppressed the increment of postprandial blood glucose levels in rats (P < 0.01), and increased the viscosity of their digesta. The insoluble fibers present in BLP might play a role in controlling blood glucose level by increasing digesta viscosity. In human, BLP suppressed the increment of postprandial blood glucose level only in those which exhibited higher blood glucose levels after meals (P < 0.01). BLP might suppress the increment of postprandial blood glucose level by increasing digesta viscosity in both of rats and humans who require blood glucose monitoring.

17.
Plant Signal Behav ; 5(12): 1602-6, 2010 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-21139434

RESUMO

Chloroplast photorelocation movement towards weak light and away from strong light is essential for plants to adapt to the fluctuation of ambient light conditions. In the previous study, we showed that blue light receptor phototropins mediated blue light-induced chloroplast movement in Arabidopsis by regulating short actin filaments localized at the chloroplast periphery (cp-actin filaments) rather than actin cables in the cytoplasm. However, the signaling pathway for the chloroplast photorelocation movement is still unclear. We also identified JAC1 (J-domain protein required for chloroplast accumulation response 1) as an essential component for the accumulation response and dark positioning in Arabidopsis. We recently determined the crystal structure of the J-domain of JAC1. The JAC1 J-domain has a positively charged surface, which forms a putative interface with the Hsc70 chaperone by analogy to that of bovine auxilin. Furthermore, the mutation of the highly conserved HPD motif in the JAC1 J-domain impaired the in vivo activity of JAC1. These data suggest that JAC1 cochaperone activity with HSC70 is essential for chloroplast photorelocation movement.


Assuntos
Cloroplastos/metabolismo , Chaperonas Moleculares/metabolismo , Proteínas de Plantas/metabolismo , Sequência de Aminoácidos , Transporte Biológico , Endocitose , Proteínas de Choque Térmico HSC70/metabolismo , Modelos Moleculares , Dados de Sequência Molecular , Proteínas de Plantas/química , Homologia de Sequência de Aminoácidos , Relação Estrutura-Atividade
18.
Photosynth Res ; 98(1-3): 159-67, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18425599

RESUMO

The redox potential of Q(A) in photosystem II (PSII) is known to be lower by approximately 100 mV in the presence of phenolic herbicides compared with the presence of DCMU-type herbicides. In this study, the structural basis underlying the herbicide effects on the Q(A) redox potential was studied using Fourier transform infrared (FTIR) spectroscopy. Light-induced Q(A)(-)/Q(A) FTIR difference spectra of Mn-depleted PSII membranes in the presence of DCMU, atrazine, terbutryn, and bromacil showed a strong CO stretching peak of Q(A)(-) at 1,479 cm(-1), while binding of phenolic herbicides, bromoxynil and ioxynil, induced a small but clear downshift by approximately 1 cm(-1). The CO peak positions and the small frequency difference were reproduced in the S(2)Q(A)(-)/S(1)Q(A) spectra of oxygen-evolving PSII membranes with DCMU and bromoxynil. The relationship of the CO frequency with herbicide species correlated well with that of the peak temperatures of thermoluminescence due to S(2)Q(A)(-) recombination. Density functional theory calculations of model hydrogen-bonded complexes of plastoquinone radical anion showed that the small shift of the CO frequency is consistent with a change in the hydrogen-bond structure most likely as a change in its strength. The Q(A)(-)/Q(A) spectra in the presence of bromoxynil, and ioxynil, which bear a nitrile group in the phenolic ring, also showed CN stretching bands around 2,210 cm(-1). Comparison with the CN frequencies of bromoxynil in solutions suggested that the phenolic herbicides take a phenotate anion form in the Q(B) pocket. It was proposed that interaction of the phenolic C-O(-) with D1-His215 changes the strength of the hydrogen bond between the CO of Q(A) with D2-His214 via the iron-histidine bridge, causing the decrease in the Q(A) redox potential.


Assuntos
Herbicidas/farmacologia , Complexo de Proteína do Fotossistema II/efeitos dos fármacos , Plastoquinona/metabolismo , Ligação de Hidrogênio , Oxirredução , Fotossíntese/efeitos dos fármacos , Espectroscopia de Infravermelho com Transformada de Fourier , Spinacia oleracea
19.
Science ; 309(5731): 140-2, 2005 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-15905365

RESUMO

Previous evidence suggested that transfer RNAs (tRNAs) cross the nuclear envelope to the cytosol only once after maturing in the nucleus. We now present evidence for nuclear import of tRNAs in yeast. Several export mutants accumulate mature tRNAs in the nucleus even in the absence of transcription. Import requires energy but not the Ran cycle. These results indicate that tRNAs shuttle between the nucleus and cytosol.


Assuntos
Núcleo Celular/metabolismo , Citosol/metabolismo , RNA Fúngico/metabolismo , RNA de Transferência Aminoácido-Específico/metabolismo , RNA de Transferência/metabolismo , Saccharomyces cerevisiae/metabolismo , Transporte Ativo do Núcleo Celular , Trifosfato de Adenosina/metabolismo , Núcleo Celular/genética , Íntrons , Mutação , Precursores de RNA/metabolismo , RNA de Transferência/genética , Aminoacil-RNA de Transferência/metabolismo , RNA de Transferência de Isoleucina/metabolismo , RNA de Transferência de Prolina/metabolismo , RNA de Transferência de Tirosina/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/crescimento & desenvolvimento , Transcrição Gênica , Proteína ran de Ligação ao GTP/metabolismo
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