Exploration of the Catalytic Cycle Dynamics of Vigna Radiata H+-Translocating Pyrophosphatases Through Hydrogen-Deuterium Exchange Mass Spectrometry.

Vigna radiata H+-translocating pyrophosphatases (VrH+-PPases, EC 3.6.1.1) are present in various endomembranes of plants, bacteria, archaea, and certain protozoa. They transport H+ into the lumen by hydrolyzing pyrophosphate, which is a by-product of many essential anabolic reactions. Although the crystal structure of H+-PPases has been elucidated, the H+ translocation mechanism of H+-PPases in the solution state remains unclear. In this study, we used hydrogen-deuterium exchange (HDX) coupled with mass spectrometry (MS) to investigate the dynamics of H+-PPases between the previously proposed R state (resting state, Apo form), I state (intermediate state, bound to a substrate analog), and T state (transient state, bound to inorganic phosphate). When hydrogen was replaced by proteins in deuterium oxide solution, the backbone hydrogen atoms, which were exchanged with deuterium, were identified through MS. Accordingly, we used deuterium uptake to examine the structural dynamics and conformational changes of H+-PPases in solution. In the highly conserved substrate binding and proton exit regions, HDX-MS revealed the existence of a compact conformation with deuterium exchange when H+-PPases were bound with a substrate analog and product. Thus, a novel working model was developed to elucidate the in situ catalytic mechanism of pyrophosphate hydrolysis and proton transport. In this model, a proton is released in the I state, and the TM5 inner wall serves as a proton piston.

Overexpression of a multifunctional ß-glucosidase gene from thermophilic archaeon Sulfolobus solfataricus in transgenic tobacco could facilitate glucose release and its use as a reporter.

The ß-glucosidase, which hydrolyzes the ß(1-4) glucosidic linkage of disaccharides, oligosaccharides and glucose-substituted molecules, has been used in many biotechnological applications. The current commercial source of ß-glucosidase is mainly microbial fermentation. Plants have been developed as bioreactors to produce various kinds of proteins including ß-glucosidase because of the potential low cost. Sulfolobus solfataricus is a thermoacidophilic archaeon that can grow optimally at high temperature, around 80 °C, and pH 2-4. We overexpressed the ß-glucosidase gene from S. solfataricus in transgenic tobacco via Agrobacteria-mediated transformation. Three transgenic tobacco lines with ß-glucosidase gene expression driven by the rbcS promoter were obtained, and the recombinant proteins were accumulated in chloroplasts, endoplasmic reticulum and vacuoles up to 1%, 0.6% and 0.3% of total soluble protein, respectively. By stacking the transgenes via crossing distinct transgenic events, the level of ß-glucosidase in plants could further increase. The plant-expressed ß-glucosidase had optimal activity at 80 °C and pH 5-6. In addition, the plant-expressed ß-glucosidase showed high thermostability; on heat pre-treatment at 80 °C for 2 h, approximately 70% residual activity remained. Furthermore, wind-dried leaf tissues of transgenic plants showed good stability in short-term storage at room temperature, with ß-glucosidase activity of about 80% still remaining after 1 week of storage as compared with fresh leaf. Furthermore, we demonstrated the possibility of using the archaebacterial ß-glucosidase gene as a reporter in plants based on alternative ß-galactosidase activity.

Potassium Stimulation of IAA Transport Mediated by the Arabidopsis Importer AUX1 Investigated in a Heterologous Yeast System.

Auxin regulates diverse processes involved in plant growth and development. AUX1 is the first identified and most widely investigated auxin importer, and plays an important role in root gravitropism and the development of lateral root and root hair. However, the regulation of auxin transport by AUX1 is still not well understood. In this study, we examined the effect of metal ions on AUX1 transport function and found that the activity could be specifically stimulated four times by K+. Further experiments revealed the preference of KF on the enhancement of transport activity of AUX1 over KCl, KBr, and KI. In addition, the interaction between K+ and AUX1 confers AUX1 more resistant to thermal stress but more vulnerable to proteolysis. Conventional chemical modification indicated that the extracellular acidic amino acids of AUX1 play a key role in the K+ stimulation. Site-specific mutagenesis showed that the replacement of Asp166, Asp293, and Asp312 of AUX1 to alanine deteriorated the K+-stimulated auxin transport. By contrast, when these residues were mutated to glutamate, lysine, or asparagine, only the D312E variant restored the IAA transport activity to the wild-type level. It is thus convinced that D312 is presumably the most promising residue for the K+ stimulation on AUX1.

Dual-focal-plane augmented reality head-up display using a single picture generation unit and a single freeform mirror.

Two or more focal planes are required in augmented reality head-up displays (AR HUDs) to respectively present basic and interactive driving information to car drivers; whereas, solutions using two separated picture generation units (PGUs) with two sets of optics incur increased cost, reduced reliability, and expanded volume. To develop an AR HUD using a single PGU and a single curved mirror, we propose to set two logically separated regions on a single PGU and optically relay one of them to a new position to create two focal planes. A single freeform mirror acquired through careful optical and mechanical design optimization produces high image quality in an eyebox of 120 mm by 60 mm, simultaneously for a far image (9 m, 10° by 3°) and a near image (2.5 m, 6° by 2°). Finally, an AR HUD product with a compact volume of 8.5 L is fabricated to experimentally verify the design.

Crystal structure of a membrane-embedded H+-translocating pyrophosphatase.

H(+)-translocating pyrophosphatases (H(+)-PPases) are active proton transporters that establish a proton gradient across the endomembrane by means of pyrophosphate (PP(i)) hydrolysis. H(+)-PPases are found primarily as homodimers in the vacuolar membrane of plants and the plasma membrane of several protozoa and prokaryotes. The three-dimensional structure and detailed mechanisms underlying the enzymatic and proton translocation reactions of H(+)-PPases are unclear. Here we report the crystal structure of a Vigna radiata H(+)-PPase (VrH(+)-PPase) in complex with a non-hydrolysable substrate analogue, imidodiphosphate (IDP), at 2.35 Å resolution. Each VrH(+)-PPase subunit consists of an integral membrane domain formed by 16 transmembrane helices. IDP is bound in the cytosolic region of each subunit and trapped by numerous charged residues and five Mg(2+) ions. A previously undescribed proton translocation pathway is formed by six core transmembrane helices. Proton pumping can be initialized by PP(i) hydrolysis, and H(+) is then transported into the vacuolar lumen through a pathway consisting of Arg 242, Asp 294, Lys 742 and Glu 301. We propose a working model of the mechanism for the coupling between proton pumping and PP(i) hydrolysis by H(+)-PPases.

Squeezing at entrance of proton transport pathway in proton-translocating pyrophosphatase upon substrate binding.

Homodimeric proton-translocating pyrophosphatase (H(+)-PPase; EC 3.6.1.1) is indispensable for many organisms in maintaining organellar pH homeostasis. This unique proton pump couples the hydrolysis of PPi to proton translocation across the membrane. H(+)-PPase consists of 14-16 relatively hydrophobic transmembrane domains presumably for proton translocation and hydrophilic loops primarily embedding a catalytic site. Several highly conserved polar residues located at or near the entrance of the transport pathway in H(+)-PPase are essential for proton pumping activity. In this investigation single molecule FRET was employed to dissect the action at the pathway entrance in homodimeric Clostridium tetani H(+)-PPase upon ligand binding. The presence of the substrate analog, imidodiphosphate mediated two sites at the pathway entrance moving toward each other. Moreover, single molecule FRET analyses after the mutation at the first proton-carrying residue (Arg-169) demonstrated that conformational changes at the entrance are conceivably essential for the initial step of H(+)-PPase proton translocation. A working model is accordingly proposed to illustrate the squeeze at the entrance of the transport pathway in H(+)-PPase upon substrate binding.

Functional and fluorescence analyses of tryptophan residues in H+-pyrophosphatase of Clostridium tetani.

Homodimeric proton-translocating pyrophosphatase (H+-PPase; EC 3.6.1.1) maintains the cytoplasmic pH homeostasis of many bacteria and higher plants by coupling pyrophosphate (PPi) hydrolysis and proton translocation. H+-PPase accommodates several essential motifs involved in the catalytic mechanism, including the PPi binding motif and Acidic I and II motifs. In this study, 3 intrinsic tryptophan residues, Trp-75, Trp-365, and Trp-602, in H+-PPase from Clostridium tetani were used as internal probes to monitor the local conformational state of the periplasm domain, transmembrane region, and cytoplasmic domain, respectively. Upon binding of the substrate analog Mg-imidodiphosphate (Mg-IDP), local structural changes prevented the modification of tryptophan residues by N-bromosuccinimide (NBS), especially at Trp-602. Following Mg-Pi binding, Trp-75 and Trp-365, but not Trp-602, were slightly protected from structural modifications by NBS. These results reveal the conformation of H+-PPase is distinct in the presence of different ligands. Moreover, analyses of the Stern-Volmer relationship and steady-state fluorescence anisotropy also indicate that the local structure around Trp-602 is more exposed to solvent and varied under different environments. In addition, Trp-602 was identified to be a crucial residue in the H+-PPase that may potentially be involved in stabilizing the structure of the catalytic region by site-directed mutagenesis analysis.

Dynamic expression of cathepsin L in the black soldier fly (Hermetia illucens) gut during Escherichia coli challenge.

The black soldier fly (BSF), Hermetia illucens, has the potential to serve as a valuable resource for waste bioconversion due to the ability of the larvae to thrive in a microbial-rich environment. Being an ecological decomposer, the survival of BSF larvae (BSFL) relies on developing an efficient defense system. Cathepsin L (CTSL) is a cysteine protease that plays roles in physiological and pathological processes. In this study, the full-length of CTSL was obtained from BSF. The 1,020-bp open reading frame encoded a preprotein of 339 amino acids with a predicted molecular weight of 32 kDa. The pro-domain contained the conserved ERFNIN, GNYD, and GCNGG motifs, which are all characteristic of CTSL. Homology revealed that the deduced amino acid sequence of BSF CTSL shared 74.22-72.99% identity with Diptera flies. Immunohistochemical (IHC) analysis showed the CTSL was predominantly localized in the gut, especially in the midgut. The mRNA expression of CTSL in different larval stages was analyzed by quantitative real-time PCR (RT-qPCR), which revealed that CTSL was expressed in the second to sixth instar, with the highest expression in the fifth instar. Following an immune challenge in vivo using Escherichia coli (E. coli), CTSL mRNA was significantly up-regulated at 6 h post-stimulation. The Z-Phe-Arg-AMC was gradually cleaved by the BSFL extract after 3 h post-stimulation. These results shed light on the potential role of CTSL in the defense mechanism that helps BSFL to survive against pathogens in a microbial-rich environment.

A hierarchical model of accelerating factors to promote urban renewal and reconstruction of unsafe and old buildings.

The issue of urban renewal is complex and multifaceted. In this study, six specialists in the construction industry were invited to conduct audio interviews, which were compiled into verbatim text. The key phrases were extracted by Grounded theory, and three levels of coding were retrieved. The data were categorized into ten accelerating urban renewal factors in three constructs to establish an Analytic Hierarchy Process framework. Using institutional theory to construct outcomes based on grounded theory, transforming these into specific urban renewal relation issue elements. 113 AHP questionnaires were collected from five types of specialists, including practitioners, professionals, participants in urban renewal, academics, and government staff. The results show that relaxing the plot ratio control and incentives is ranked No. 1 by practitioners, participants in urban renewal, professionals, and academics, indicating that the factor is highly valued by specialists but neglected by government staff. Secondly, practitioners, academics, participants in urban renewal, and professionals identified incentives and rewards for urban renewal and enhancing the trust and credibility of urban renewal projects as crucial factors. However, the government staff showed a different weighting. This indicates that government staff is determined to accelerate urban renewal. Finally, the suggestion of this study is in line with the views of the specialists interviewed, who suggest that the government should hold public hearings regularly and seriously to listen to people and specialists. Only through public hearings can all parties reach a consensus. The government should consolidate the views of all parties to amend or enact a bill on urban renewal that is more in line with the changes of the times, including appropriately relaxing the control of building plot ratio and other accelerating factors, to promote urban renewal in Taiwan.

Functional investigation of transmembrane helix 3 in H⁺-translocating pyrophosphatase.

H⁺-translocating pyrophosphatase (H⁺-PPase, EC 3.6.1.1) plays an important role in acidifying vacuoles by transporting protons across membranes at the expense of pyrophosphate (PP(i)) hydrolysis. Vigna radiata H⁺-PPase (VrH⁺-PPase) contains 16 transmembrane helices (TMs). The hydrophobicity of TM3 is relatively lower than that of most other TMs, and the amino acids in this TM are highly conserved in plants. Furthermore, TM5 and -6, which are the core TMs involving in H⁺-PPase functions, are near TM3. It is thus proposed that TM3 is associated with H⁺-PPase activity. To address this possibility, site-directed mutagenesis was applied in this investigation to determine the role of TM3 in VrH⁺-PPase. Upon alanine/serine substitution, T138 and S142, whose side chains face toward the center TMs, were found to be involved in efficient proton transport. G149/S153 and G160/A164 pairs at the crucial termini of the two GxxxG-like motifs are indispensable in maintaining enzymatic activities and conformational stability. Moreover, stability in the vicinity surrounding G149 is pivotal for efficient expression. S153, M161 and A164 are critical for the K⁺-mediated stimulation of H⁺-PPase. Taken together, our results demonstrate that TM3 plays essential roles in PP(i) hydrolysis, proton transport, expression, and K⁺ stimulation of H⁺-PPase.

scDrug: From single-cell RNA-seq to drug response prediction.

Single-cell RNA sequencing (scRNA-seq) technology allows massively parallel characterization of thousands of cells at the transcriptome level. scRNA-seq is emerging as an important tool to investigate the cellular components and their interactions in the tumor microenvironment. scRNA-seq is also used to reveal the association between tumor microenvironmental patterns and clinical outcomes and to dissect cell-specific effects of drug treatment in complex tissues. Recent advances in scRNA-seq have driven the discovery of biomarkers in diseases and therapeutic targets. Although methods for prediction of drug response using gene expression of scRNA-seq data have been proposed, an integrated tool from scRNA-seq analysis to drug discovery is required. We present scDrug as a bioinformatics workflow that includes a one-step pipeline to generate cell clustering for scRNA-seq data and two methods to predict drug treatments. The scDrug pipeline consists of three main modules: scRNA-seq analysis for identification of tumor cell subpopulations, functional annotation of cellular subclusters, and prediction of drug responses. scDrug enables the exploration of scRNA-seq data readily and facilitates the drug repurposing process. scDrug is freely available on GitHub at https://github.com/ailabstw/scDrug.

MetaMOPE: a web service for mobile phase determination and fast chromatography peaks evaluation for metabolomics.

Motivation: Liquid chromatography coupled with mass spectrometry (LC-MS) is widely used in metabolomics studies, while HILIC LC-MS is particularly suited for polar metabolites. Determining an optimized mobile phase and developing a proper liquid chromatography method tend to be laborious, time-consuming and empirical. Results: We developed a containerized web tool providing a workflow to quickly determine the optimized mobile phase by batch-evaluating chromatography peaks for metabolomics LC-MS studies. A mass chromatographic quality value, an asymmetric factor, and the local maximum intensity of the extracted ion chromatogram were calculated to determine the number of peaks and peak retention time. The optimal mobile phase can be quickly determined by selecting the mobile phase that produces the largest number of resolved peaks. Moreover, the workflow enables one to automatically process the repeats by evaluating chromatography peaks and determining the retention time of large standards. This workflow was validated with 20 chemical standards and successfully constructed a reference library of 571 metabolites for the HILIC LC-MS platform. Availability and implementation: MetaMOPE is freely available at https://metamope.cmdm.tw. Source code and installation instructions are available on GitHub: https://github.com/CMDM-Lab/MetaMOPE. Supplementary information: Supplementary data are available at Bioinformatics Advances online.

Crystal structures of dimeric and heptameric mtHsp60 reveal the mechanism of chaperonin inactivation.

Mitochondrial Hsp60 (mtHsp60) plays a crucial role in maintaining the proper folding of proteins in the mitochondria. mtHsp60 self-assembles into a ring-shaped heptamer, which can further form a double-ring tetradecamer in the presence of ATP and mtHsp10. However, mtHsp60 tends to dissociate in vitro, unlike its prokaryotic homologue, GroEL. The molecular structure of dissociated mtHsp60 and the mechanism behind its dissociation remain unclear. In this study, we demonstrated that Epinephelus coioides mtHsp60 (EcHsp60) can form a dimeric structure with inactive ATPase activity. The crystal structure of this dimer reveals symmetrical subunit interactions and a rearranged equatorial domain. The α4 helix of each subunit extends and interacts with its adjacent subunit, leading to the disruption of the ATP-binding pocket. Furthermore, an RLK motif in the apical domain contributes to stabilizing the dimeric complex. These structural and biochemical findings provide new insights into the conformational transitions and functional regulation of this ancient chaperonin.

Structural basis for calcium-stimulating pore formation of Vibrio α-hemolysin.

Vibrio α-hemolysins (αHLs) are ß-pore-forming toxins secreted by Vibrio pathogens, crucial for the facilitation of bacterial infections through host cell lysis. These toxins are produced as inactive precursors, requiring proteolytic maturation and membrane association for activation within host tissues. Here, we investigate Vibrio campbellii αHL (VcαHL), and establish that its hemolytic activity is significantly stimulated by calcium ions, with an EC50 that aligns with physiological calcium concentrations. Furthermore, we illustrate the vital contribution of calcium ions to the oligomerization of VcαHL on membranes. Using X-ray crystallography and cryo-electron microscopy, we decipher both the immature and assembled structures of VcαHL and elucidate the conformational changes corresponding to toxin assembly. We also identify a calcium-binding module that is integral for VcαHL's calcium-dependent activation. These findings provide insights into the regulatory mechanisms of VcαHL and have the potential to inform the development of targeted therapeutic strategies against Vibrio infections.

Identification of essential lysines involved in substrate binding of vacuolar H+-pyrophosphatase.

H+-translocating pyrophosphatase (H+-PPase; EC 3.6.1.1) drives proton transport against an electrochemical potential gradient by hydrolyzing pyrophosphate (PPi) and is found in various endomembranes of higher plants, bacteria, and some protists. H+-PPase contains seven highly conserved lysines. We examined the functional roles of these lysines, which are, for the most part, found in the cytosolic regions of mung bean H+-PPase by site-directed mutagenesis. Construction of mutants that each had a cytosolic and highly conserved lysine substituted with an alanine resulted in dramatic drops in the PPi hydrolytic activity. The effects caused by ions on the activities of WT and mutant H+-PPases suggest that Lys-730 may be in close proximity to the Mg2+-binding site, and the great resistance of the K694A and K695A mutants to fluoride inhibition suggests that these lysines are present in the active site. The modifier fluorescein 5'-isothiocyanate (FITC) labeled a lysine at the H+-PPase active site but did not inhibit the hydrolytic activities of K250A, K250N, K250T, and K250S, which suggested that Lys-250 is essential for substrate binding and may be involved in proton translocation. Analysis of tryptic digests indicated that Lys-711 and Lys-717 help maintain the conformation of the active site. Proteolytic evidence also demonstrated that Lys-250 is the primary target of trypsin and confirmed its crucial role in H+-PPase hydrolysis.

The transmembrane domain 6 of vacuolar H(+)-pyrophosphatase mediates protein targeting and proton transport.

Vacuolar H(+)-pyrophosphatase (V-PPase; EC 3.6.1.1) plays a significant role in the maintenance of the pH in cytoplasm and vacuoles via proton translocation from the cytosol to the vacuolar lumen at the expense of PP(i) hydrolysis. The topology of V-PPase as predicted by TopPred II suggests that the catalytic site is putatively located in loop e and exposed to the cytosol. The adjacent transmembrane domain 6 (TM6) is highly conserved and believed to participate in the catalytic function and conformational stability of V-PPase. In this study, alanine-scanning mutagenesis along TM6 of the mung bean V-PPase was carried out to identify its structural and functional role. Mutants Y299A, A306S and L317A exhibited gross impairment in both PP(i) hydrolysis and proton translocation. Meanwhile, mutations at L307 and N318 completely abolished the targeting of the enzyme, causing broad cytosolic localization and implicating a possible role of these residues in protein translocation. The location of these amino acid residues was on the same side of the helix wheel, suggesting their involvement in maintaining the stability of enzyme conformation. G297A, E301A and A305S mutants showed declines in proton translocation but not in PP(i) hydrolysis, consequently resulting in decreases in the coupling efficiency. These amino acid residues cluster at one face of the helix wheel, indicating their direct/indirect participation in proton translocation. Taken together, these data indicate that TM6 is crucial to vacuolar H(+)-pyrophosphatase, probably mediating protein targeting, proton transport, and the maintenance of enzyme structure.

Evaluation of an automated dental unit water system's contamination control protocol.

BACKGROUND: This study addresses the efficacy of an automated decontamination protocol using the germicide 'tetra acetyl ethylene diamine (TAED) perborate' (Farmec SpA, Italy). The germicide TAED perborate protocol is used in the Castellini Dental Units fitted with an Autosteril unit (an automated device that can cycle 0.26% TAED perborate solution and sterile water for cleaning the water system between patients and overnight). Prior to testing the Autosteril and the 0.26% TAED perborate protocol on the Logos Jr Dental Unit (Castellini SpA, Italy), TAED perborate was used on a dental unit water system simulation device. METHODS: A dental unit water system simulation device equipped with four dental unit water systems and with naturally grown and mature biofilm contamination was used in this study (three treatment units and one control). One treatment group used a simulated 5 minutes contact with TAED perborate and sterile water for irrigation; the second used a simulated 5 minutes contact with TAED perborate and 2 ppm ClO2 for irrigation; the third used a simulated 5 minutes contact with TAED perborate and municipal water for irrigation. The control group used municipal water for irrigation with no cleaning/disinfection protocols. This protocol was repeated for 30 cycles. Laser scanning confocal microscopy (LSCM) was used to study the effects on natural and mature biofilms, and R2A agar used to quantify heterotrophic plate counts in the effluent irrigant. Antimicrobial efficacy was evaluated by challenging TAED perborate with microbes and spores (M. smegmatis and B. subtilis). Deleterious effects of the germicide were evaluated on metal and nonmetal parts of dental unit water systems. Heterotrophic plate counts using R2A agar and LSCM of the lines were conducted to assess biofilm and microbial control. RESULTS: Baseline water samples showed mean contamination >5.6 log10 cfu/ml. After initial cleaning, all three groups maintained mean contamination levels of less than 1.1 (SD <0.3) log10 cfu/ml. LSCM of baseline samples was positive for live biofilm in all groups. At the end of the study, viable biofilm was only present in the control. In the microbial challenge test, all vegetative organisms were killed within 30 seconds of contact, while spores were killed within 5 minutes. Corrosion was seen in metals used in US-manufactured dental unit materials, while not observed in those used in the Castellini Logos Jr dental unit. CONCLUSION: In this study, the TAED perborate protocol was effective in biofilm control and control of dental treatment water contamination. Use of sterile water or 2 ppm ClO2 along with TAED treatment also controlled planktonic contamination effectively. CLINICAL SIGNIFICANCE: Environmental biofilms contaminate dental unit water systems over time and affect the quality of dental treatment water. Contaminants include environmental biofilms, microbes, including gram-negative rods and endotoxins in high doses that are not of acceptable quality for treating patients. There are many germicidal protocols for treating this contamination and one such is the prescribed use of TAED perborate used in conjunction with sterile water for irrigation in the autosteril device, an integral component of the Castellini dental units for between patient decontamination of dental unit water systems. This study was conducted on an automated simulation dental unit water system to test the TAED perborate protocol's efficacy on naturally grown, mature environmental biofilms, it's efficacy on microbes and spores and it's effects on materials used in dental unit water systems. This translational research addresses both microbial control and material effects of TAED perborate in studying efficacy and possible deleterious effects and simulated use in dentistry. Currently, this antimicrobial use protocol is followed worldwide in the Castellini dental units that are used in day-to-day dental patient care.

Transport efficiency of AtGTR1 dependents on the hydrophobicity of transported glucosinolates.

Glucosinolates (GLSs) are a group of secondary metabolites that are involved in the defense of herbivores. In Arabidopsis thaliana, Glucosinolate Transporter 1 (AtGTR1) transports GLSs with high affinity via a proton gradient-driven process. In addition to transporting GLSs, AtGTR1 also transports phytohormones, jasmonic acid-isoleucine (JA-Ile), and gibberellin (GA). However, little is known about the mechanisms underlying the broad substrate specificity of AtGTR1. Here, we characterized the substrate preference of AtGTR1 by using a yeast uptake assay, and the results revealed that GLS transport rates are negatively correlated with the hydrophobicity of substrates. Interestingly, the AtGTR1 showed a higher substrate affinity for GLSs with higher hydrophobicity, suggesting a hydrophobic substrate binding pocket. In addition, competition assays revealed that JA, salicylic acid (SA), and indole-3-acetic acid (IAA) competed with GLS for transport in yeast, suggesting a potential interaction of AtGTR1 with these phytohormones. To further characterize the functional properties of AtGTR1, mutagenesis experiments confirmed that the conserved EXXEK motif and Arg166 are essential for the GLS transport function. In addition, the purified AtGTR1 adopts a homodimeric conformation, which is possibly regulated by phosphorylation on Thr105. The phosphomimetic mutation, T105D, reduced its protein expression and completely abrogated its GLS transport function, indicating the essential role of phosphorylation on AtGTR1. In summary, this study investigated various factors associated with the GLS transport and increased our knowledge on the substrate preferences of AtGTR1. These findings contribute to understanding how the distribution of defense GLSs is regulated in plants and could be used to improve crop quality in agriculture.

To join the rebuild or not? An exploration of the factors influencing the public's intention to participate in urban renewal.

Due to the lack of trust in the builder and indeterminate benefits, it is a struggle for people in Taiwan to make up their minds to participate in urban renewal. This leads to the completion rate of urban renewal of fewer than one ten-thousandth of the new construction needed. This study investigated the perspective on the research variables for people in Taiwan and how those influence their intention to participate in urban renewal. Using the Theory of Planned Behavior, the research framework is designed with the trust of urban renewal project builders and the perceived benefits of public participation as the independent variables. Attitudes, subjective norms, and perceived behavioral control are the mediating variables, and the general public's intention to participate in urban renewal is the dependent variable. A total of 545 valid questionnaires were collected through the survey. The results showed that the respondents' trust in the builder of the urban renewal project positively and significantly influenced their perceived benefits of the project, and the respondents' trust in the builder significantly influenced their subjective norms. The perceived benefits positively and significantly affected their attitudes and subjective norms, and people's attitudes, subjective norms, and perceived behavioral control positively and significantly affected their intention to participate in urban renewal. People's perceived benefits in urban renewal projects affected their participation intention through attitudes and subjective norms. The variable perceived benefits most strongly influenced people's intention to participate in urban renewal in this study. This study provides practical suggestions for the government and builders to increase people's intention to participate in urban renewal. This study modeled two independent variables, trust in the builder and perceived benefits, under the urban renewal context in Taiwan. In future works, other factors could be included, such as tax incentives, floor area rewards, and fair appraisal.

Distance variations between active sites of H(+)-pyrophosphatase determined by fluorescence resonance energy transfer.

Homodimeric H(+)-pyrophosphatase (H(+)-PPase; EC 3.6.1.1) is a unique enzyme playing a pivotal physiological role in pH homeostasis of organisms. This novel H(+)-PPase supplies energy at the expense of hydrolyzing metabolic byproduct, pyrophosphate (PP(i)), for H(+) translocation across membrane. The functional unit for the translocation is considered to be a homodimer. Its putative active site on each subunit consists of PP(i) binding motif, Acidic I and II motifs, and several essential residues. In this investigation structural mapping of these vital regions was primarily determined utilizing single molecule fluorescence resonance energy transfer. Distances between two C termini and also two N termini on homodimeric subunits of H(+)-PPase are 49.3 + or - 4.0 and 67.2 + or - 5.7 A, respectively. Furthermore, putative PP(i) binding motifs on individual subunits are found to be relatively far away from each other (70.8 + or - 4.8 A), whereas binding of potassium and substrate analogue led them to closer proximity. Moreover, substrate analogue but not potassium elicits significant distance variations between two Acidic I motifs and two His-622 residues on homodimeric subunits. Taken together, this study provides the first quantitative measurements of distances between various essential motifs, residues, and putative active sites on homodimeric subunits of H(+)-PPase. A working model is accordingly proposed elucidating the distance variations of dimeric H(+)-PPase upon substrate binding.