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El Salamouni NS, Buckley BJ, Lee R, Ranson M, Kelso MJ, Yu H. Ion Transport and Inhibitor Binding by Human NHE1: Insights from Molecular Dynamics Simulations and Free Energy Calculations. J Phys Chem B 2024; 128:440-450. [PMID: 38185879 DOI: 10.1021/acs.jpcb.3c05863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
The human Na+/H+ exchanger (NHE1) plays a crucial role in maintaining intracellular pH by regulating the electroneutral exchange of a single intracellular H+ for one extracellular Na+ across the plasma membrane. Understanding the molecular mechanisms governing ion transport and the binding of inhibitors is of importance in the development of anticancer therapeutics targeting NHE1. In this context, we performed molecular dynamics (MD) simulations based on the recent cryo-electron microscopy (cryo-EM) structures of outward- and inward-facing conformations of NHE1. These simulations allowed us to explore the dynamics of the protein, examine the ion-translocation pore, and confirm that Asp267 is the ion-binding residue. Our free energy calculations did not show a significant difference between Na+ and K+ binding at the ion-binding site. Consequently, Na+ over K+ selectivity cannot be solely explained by differences in ion binding. Our MD simulations involving NHE1 inhibitors (cariporide and amiloride analogues) maintained stable interactions with Asp267 and Glu346. Our study highlights the importance of the salt bridge between the positively charged acylguanidine moiety and Asp267, which appears to play a role in the competitive inhibitory mechanism for this class of inhibitors. Our computational study provides a detailed mechanistic interpretation of experimental data and serves the basis of future structure-based inhibitor design.
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Affiliation(s)
- Nehad S El Salamouni
- School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
- Molecular Horizons, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Benjamin J Buckley
- School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
- Molecular Horizons, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Richmond Lee
- School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
- Molecular Horizons, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Marie Ranson
- School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
- Molecular Horizons, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Michael J Kelso
- School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
- Molecular Horizons, University of Wollongong, Wollongong, NSW 2522, Australia
| | - Haibo Yu
- School of Chemistry and Molecular Bioscience, University of Wollongong, Wollongong, NSW 2522, Australia
- Molecular Horizons, University of Wollongong, Wollongong, NSW 2522, Australia
- ARC Centre of Excellence in Quantum Biotechnology, University of Wollongong, Wollongong, NSW 2522, Australia
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Meng Q, Luo L, Lei M, Chen Z, Sun Y, Chen X, Zhai Z, Zhang Y, Cao J, Su Z, Li F, Li J, Hong A, Chen X. Inhibition of FGFR2 Signaling by Cynaroside Attenuates Liver Fibrosis. Pharmaceuticals (Basel) 2023; 16:ph16040548. [PMID: 37111305 PMCID: PMC10145669 DOI: 10.3390/ph16040548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 03/16/2023] [Accepted: 03/24/2023] [Indexed: 04/09/2023] Open
Abstract
Liver fibrosis represents a significant health hazard with a high morbidity rate and an increased risk of liver cancer. Targeting overactivated Fibroblast growth factor receptor 2 (FGFR2) is a promising strategy to counteract collagen accumulation during liver fibrosis. However, there is a shortage of drugs to specifically block the activation of FGFR2 in liver fibrosis patients. Data mining, cell validation, and animal studies showed a positive correlation between FGFR2 overexpression and liver fibrosis development. Novel FGFR2 inhibitors were screened using a microarray-based high-throughput binding analysis. The effectiveness of each candidate was validated through simulated docking, binding affinity verification, single-point mutation validation, and in vitro kinase inhibition measurements to demonstrate the ability of each inhibitor to block the catalytic pocket and reverse FGFR2 overactivation. A specific FGFR2 inhibitor, cynaroside (CYN, also known as luteoloside), was screened based on the finding that FGFR2 promotes hepatic stellate cell (HSC) activation and collagen secretion in hepatocytes. The results from cellular assays showed that CYN can inhibit FGFR2 hyperactivation resulting from its overexpression and excessive basic fibroblast growth factor (bFGF), reducing HSC activation and collagen secretion in hepatocytes. Animal experiments on a carbon tetrachloride (CCl4) mouse model and a nonalcoholic steatohepatitis mouse model indicate that CYN treatment reduces liver fibrosis during fibrosis formation. These findings suggest that CYN prevents liver fibrosis formation at the cell level and in mouse models.
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Affiliation(s)
- Qilin Meng
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
| | - Lin Luo
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
| | - Minghua Lei
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
| | - Zhiqi Chen
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
| | - Yuanmeng Sun
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
| | - Xue Chen
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
| | - Zhaodong Zhai
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
| | - Yibo Zhang
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
| | - Jieqiong Cao
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
| | - Zijian Su
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
| | - Fu Li
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
| | - Jingsheng Li
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
| | - An Hong
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
| | - Xiaojia Chen
- Department of Cell Biology, College of Life Science and Technology, Jinan University, Guangzhou 510632, China
- National Engineering Research Center of Genetic Medicine, Guangzhou 510632, China
- Guangdong Province Key Laboratory of Bioengineering Medicine, Guangzhou 510632, China
- Guangdong Provincial Biotechnology Drug & Engineering Technology Research Center, Guangzhou 510632, China
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The Na+/H+ Exchanger NHX1 Controls H+ Accumulation in the Vacuole to Influence Sepal Color in Hydrangea macrophylla. INTERNATIONAL JOURNAL OF PLANT BIOLOGY 2023. [DOI: 10.3390/ijpb14010022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/25/2023] Open
Abstract
Hydrangea macrophylla is popular for its unique physiological characteristics and changeable colors. Previous studies have shown that the pH of the vacuoles of the sepal cells of hydrangea affects the color of the sepals. Located on the vacuolar membrane, NHX1 is an important H+ proton pump that drives the exchange of metal ions. This proton pump affects the physiological environment by controlling the accumulation of H+ in the vacuole. In hydrangea, the HmNHX1 gene has an open reading frame of 1626 bp and encodes a total of 541 amino acids. Bioinformatic analysis showed that HmNHX1, which encodes a Na+/H+ exchanger, is located on the vacuolar membrane. Tissue-specific expression analysis showed that the expression of this gene in the treatment group was higher than that in the control group. The ion flux in the vacuoles of colored hydrangea in the treatment group and the control group were measured, and the results showed that HmNHX1 was indeed a Na+/H+ exchanger. When the results of the HmNHX1 expression analysis and ion flux measurements are combined, it can be seen that HmNHX1 regulates the accumulation of H+ in the vacuole, ultimately affecting the color of the plant.
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Li Y, Li H, Gao J, Niu B, Wang H, Wang W. Visualizing the Intermittent Gating of Na + /H + Antiporters in Single Native Bioluminescent Bacteria. Angew Chem Int Ed Engl 2023; 62:e202215800. [PMID: 36562656 DOI: 10.1002/anie.202215800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Revised: 12/22/2022] [Accepted: 12/23/2022] [Indexed: 12/24/2022]
Abstract
While the intermittent gating of ion channels has been well studied for decades, dynamics of the action of secondary transporters, another major pathway for ion transmembrane transports, remains largely unexplored in living cells. Herein, intermittent blinking of the spontaneous bioluminescence (BL) from single native bacteria, P. phosphoreum, was reported, investigated and attributed to the intermittent gating of sodium/proton antiporters (NhaA) between the active and inactive conformations. Each gating event caused the rapid depolarization and recovery of membrane potential within several seconds, accompanying with the apparent BL blinking due to the transient inhibitions on the activity of the respiratory chain. Temperature-dependent measurements further obtained an activation energy barrier of the conformational change of 20.3 kJ mol-1 .
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Affiliation(s)
- Yaohua Li
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, ChemBIC (Chemistry and Biomedicine Innovation Center), Nanjing University, Nanjing, 210023, China
| | - Haoran Li
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, ChemBIC (Chemistry and Biomedicine Innovation Center), Nanjing University, Nanjing, 210023, China
| | - Jia Gao
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, ChemBIC (Chemistry and Biomedicine Innovation Center), Nanjing University, Nanjing, 210023, China
| | - Ben Niu
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, ChemBIC (Chemistry and Biomedicine Innovation Center), Nanjing University, Nanjing, 210023, China
| | - Huan Wang
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, ChemBIC (Chemistry and Biomedicine Innovation Center), Nanjing University, Nanjing, 210023, China
| | - Wei Wang
- State Key Laboratory of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, ChemBIC (Chemistry and Biomedicine Innovation Center), Nanjing University, Nanjing, 210023, China
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Winkelmann I, Uzdavinys P, Kenney IM, Brock J, Meier PF, Wagner LM, Gabriel F, Jung S, Matsuoka R, von Ballmoos C, Beckstein O, Drew D. Crystal structure of the Na +/H + antiporter NhaA at active pH reveals the mechanistic basis for pH sensing. Nat Commun 2022; 13:6383. [PMID: 36289233 PMCID: PMC9606361 DOI: 10.1038/s41467-022-34120-z] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 10/14/2022] [Indexed: 12/25/2022] Open
Abstract
The strict exchange of protons for sodium ions across cell membranes by Na+/H+ exchangers is a fundamental mechanism for cell homeostasis. At active pH, Na+/H+ exchange can be modelled as competition between H+ and Na+ to an ion-binding site, harbouring either one or two aspartic-acid residues. Nevertheless, extensive analysis on the model Na+/H+ antiporter NhaA from Escherichia coli, has shown that residues on the cytoplasmic surface, termed the pH sensor, shifts the pH at which NhaA becomes active. It was unclear how to incorporate the pH senor model into an alternating-access mechanism based on the NhaA structure at inactive pH 4. Here, we report the crystal structure of NhaA at active pH 6.5, and to an improved resolution of 2.2 Å. We show that at pH 6.5, residues in the pH sensor rearrange to form new salt-bridge interactions involving key histidine residues that widen the inward-facing cavity. What we now refer to as a pH gate, triggers a conformational change that enables water and Na+ to access the ion-binding site, as supported by molecular dynamics (MD) simulations. Our work highlights a unique, channel-like switch prior to substrate translocation in a secondary-active transporter.
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Affiliation(s)
- Iven Winkelmann
- grid.10548.380000 0004 1936 9377Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Povilas Uzdavinys
- grid.10548.380000 0004 1936 9377Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Ian M. Kenney
- grid.215654.10000 0001 2151 2636Center for Biological Physics and Department of Physics, Arizona State University, Tempe, AZ 85287 USA
| | - Joseph Brock
- grid.10548.380000 0004 1936 9377Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Pascal F. Meier
- grid.10548.380000 0004 1936 9377Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Lina-Marie Wagner
- grid.10548.380000 0004 1936 9377Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Florian Gabriel
- grid.10548.380000 0004 1936 9377Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Sukkyeong Jung
- grid.10548.380000 0004 1936 9377Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Rei Matsuoka
- grid.10548.380000 0004 1936 9377Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Christoph von Ballmoos
- grid.5734.50000 0001 0726 5157Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, 3012 Bern, Switzerland
| | - Oliver Beckstein
- grid.215654.10000 0001 2151 2636Center for Biological Physics and Department of Physics, Arizona State University, Tempe, AZ 85287 USA
| | - David Drew
- grid.10548.380000 0004 1936 9377Department of Biochemistry and Biophysics, Science for Life Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
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Prokaryotic Na+/H+ Exchangers—Transport Mechanism and Essential Residues. Int J Mol Sci 2022; 23:ijms23169156. [PMID: 36012428 PMCID: PMC9408914 DOI: 10.3390/ijms23169156] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 08/09/2022] [Accepted: 08/13/2022] [Indexed: 11/16/2022] Open
Abstract
Na+/H+ exchangers are essential for Na+ and pH homeostasis in all organisms. Human Na+/H+ exchangers are of high medical interest, and insights into their structure and function are aided by the investigation of prokaryotic homologues. Most prokaryotic Na+/H+ exchangers belong to either the Cation/Proton Antiporter (CPA) superfamily, the Ion Transport (IT) superfamily, or the Na+-translocating Mrp transporter superfamily. Several structures have been solved so far for CPA and Mrp members, but none for the IT members. NhaA from E. coli has served as the prototype of Na+/H+ exchangers due to the high amount of structural and functional data available. Recent structures from other CPA exchangers, together with diverse functional information, have allowed elucidation of some common working principles shared by Na+/H+ exchangers from different families, such as the type of residues involved in the substrate binding and even a simple mechanism sufficient to explain the pH regulation in the CPA and IT superfamilies. Here, we review several aspects of prokaryotic Na+/H+ exchanger structure and function, discussing the similarities and differences between different transporters, with a focus on the CPA and IT exchangers. We also discuss the proposed transport mechanisms for Na+/H+ exchangers that explain their highly pH-regulated activity profile.
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Lv P, Li Y, Wang R, Zhang Y, Wang W, Liu Y, Shang Y, Su D, Wang W, Yang C. The pH sensor and ion binding of NhaD Na
+
/H
+
antiporter from IT superfamily. Mol Microbiol 2022; 118:244-257. [DOI: 10.1111/mmi.14965] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2022] [Revised: 07/13/2022] [Accepted: 07/14/2022] [Indexed: 11/28/2022]
Affiliation(s)
- Peiwen Lv
- State Key Laboratory of Microbial Technology Institute of Microbial Technology, Shandong University Qingdao P. R. China
| | - Yaru Li
- State Key Laboratory of Microbial Technology Institute of Microbial Technology, Shandong University Qingdao P. R. China
| | - Ruimin Wang
- State Key Laboratory of Microbial Technology Institute of Microbial Technology, Shandong University Qingdao P. R. China
| | - Ye Zhang
- State Key Laboratory of Microbial Technology Institute of Microbial Technology, Shandong University Qingdao P. R. China
| | - Wenkai Wang
- State Key Laboratory of Microbial Technology Institute of Microbial Technology, Shandong University Qingdao P. R. China
| | - Yuanxiang Liu
- State Key Laboratory of Microbial Technology Institute of Microbial Technology, Shandong University Qingdao P. R. China
| | - Yan Shang
- State Key Laboratory of Microbial Technology Institute of Microbial Technology, Shandong University Qingdao P. R. China
| | - Dandan Su
- State Key Laboratory of Microbial Technology Institute of Microbial Technology, Shandong University Qingdao P. R. China
| | - Wei Wang
- State Key Laboratory of Microbial Technology Institute of Microbial Technology, Shandong University Qingdao P. R. China
| | - Chunyu Yang
- State Key Laboratory of Microbial Technology Institute of Microbial Technology, Shandong University Qingdao P. R. China
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Na M, Han Y, Chen Y, Ma S, Liu J, Chen X. Synthesis of Silicon Nanoparticles Emitting Yellow-Green Fluorescence for Visualization of pH Change and Determination of Intracellular pH of Living Cells. Anal Chem 2021; 93:5185-5193. [PMID: 33729748 DOI: 10.1021/acs.analchem.0c05107] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In order to understand related pathogenesis of some diseases and design new intracellular drug delivery systems, investigation of pH change in living cells in real time is important. In this paper, a new style of fluorescent silicon nanoparticles (SiNPs) as a pH-sensitive probe and for the visualization of the pH changes in cells was designed and prepared using 4-aminophenol as a reducing agent and N-aminoethyl-γ-aminopropyltrimethyl as a silicon source by a one-pot hydrothermal method. It was particularly noteworthy that the fluorescence intensity emitted from the SiNPs positively correlated with the pH value of solutions, making the SiNPs a viable probe used for sensitive sensing of pH. At the same time, a response of the probe to the pH was found in 5.0-10.0, and the SiNPs have an excellent biocompatibility (e.g., ∼74% of cell viability was remained after treatment for 24 h at 500 μg/mL of the SiNPs). The proposed method that could display the change in pH of live cells provided an effective means for visually diagnosing diseases related to intracellular pH.
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Affiliation(s)
- Min Na
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou 730000, China
| | - Yangxia Han
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou 730000, China
| | - Yonglei Chen
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou 730000, China
| | - Sudai Ma
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou 730000, China
| | - Juanjuan Liu
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou 730000, China
| | - Xingguo Chen
- State Key Laboratory of Applied Organic Chemistry and Department of Chemistry, Lanzhou University, Lanzhou 730000, China.,Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province, Lanzhou University, Lanzhou 730000, China
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9
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Quick M, Dwivedi M, Padan E. Insight into the direct interaction of Na + with NhaA and mechanistic implications. Sci Rep 2021; 11:7045. [PMID: 33782459 PMCID: PMC8007835 DOI: 10.1038/s41598-021-86318-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2020] [Accepted: 03/05/2021] [Indexed: 11/21/2022] Open
Abstract
Na+/H+ antiporters comprise a family of membrane proteins evolutionarily conserved in all kingdoms of life that are essential in cellular ion homeostasis. While several human homologues have long been drug targets, NhaA of Escherichia coli has become the paradigm for this class of secondary active transporters as NhaA crystals provided insight in the structure of this molecular machine. However, structural data revealing the composition of the binding site for Na+ (or its surrogate Li+) is missing, representing a bottleneck in our understanding of the correlation between the structure and function of NhaA. Here, by adapting the scintillation proximity assay (SPA) for direct determination of Na+ binding to NhaA, we revealed that (i) NhaA is well adapted as the main antiporter for Na+ homeostasis in Escherichia coli and possibly in other bacteria as the cytoplasmic Na+ concentration is similar to the Na+ binding affinity of NhaA, (ii) experimental conditions affect NhaA-mediated cation binding, (iii) in addition to Na+ and Li+, the halide Tl+ interacts with NhaA, (iv) whereas acidic pH inhibits maximum binding of Na+ to NhaA, partial Na+ binding by NhaA is independent of the pH, an important novel insight into the effect of pH on NhaA cation binding.
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Affiliation(s)
- Matthias Quick
- Department of Psychiatry and Center for Molecular Recognition, Columbia University Vagelos College of Physicians and Surgeons, and New York State Psychiatric Institute, New York, NY, 10032, USA.
| | - Manish Dwivedi
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904, Jerusalem, Israel.,Amity Institute of Biotechnology, Amity University Uttar Pradesh, Lucknow, 226028, India
| | - Etana Padan
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, 91904, Jerusalem, Israel.
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Dwivedi M. Site-directed mutations reflecting functional and structural properties of Ec-NhaA. Biochimie 2020; 180:79-89. [PMID: 33129932 DOI: 10.1016/j.biochi.2020.10.017] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 10/21/2020] [Accepted: 10/27/2020] [Indexed: 11/20/2022]
Abstract
NhaA antiporters are secondary integral membrane protein critical for maintaining the Na+/H+ cell homeostasis, as a result, they regulate fundamental processes like cell volume and intracellular pH. Exploration of the structural and functional properties can assist to make them effective human drug targets and mechanisms of salt-resistance in plants. NhaA proteins are integrated into cytoplasmic and intracellular membranes, transport 2H+/Na + across the membrane by the canonical alternating access mechanism. There are mutagenesis studies have done on Ec-NhaA predicting residues crucial for function and structure. The unique NhaA structural fold is formed in the middle of the membrane by two transmembrane segments (TMs), TM IV and XI which cross each other creating a delicate electrostatically balanced environment for the binding of Na+/H+. Previously, Asp164, Asp163 and Asp133 residues have been proposed as crucial for Na+/Li + binding on the based on crystal structure and mutation-based studies. However, the pathway and the binding sites for the two protons are still elusive and debatable. This review will provide comprehensive details on various mutations constructed in Ec-NhaA by different research groups using site-directed or random mutagenesis techniques. The selected residues for mutations are located on the sites which are more suspected to have a crucial role in function and structure on NhaA. This information on the single platform would accelerate further studies on the structure-function relationship on NhaA as well as will facilitate to predict the role of Na+/H+ antiporters in human diseases.
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Affiliation(s)
- Manish Dwivedi
- Amity Institute of Biotechnology, Amity University Uttar Pradesh, Gomtinagar Ext., Lucknow, 226028, India.
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11
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Methanothermobacter thermautotrophicus strain ΔH as a potential microorganism for bioconversion of CO2 to methane. J CO2 UTIL 2020. [DOI: 10.1016/j.jcou.2020.101210] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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12
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Zhang R, Abdel-Motaal H, Zou Q, Guo S, Zheng X, Wang Y, Zhang Z, Meng L, Xu T, Jiang J. A Novel MFS-MDR Transporter, MdrP, Employs D223 as a Key Determinant in the Na + Translocation Coupled to Norfloxacin Efflux. Front Microbiol 2020; 11:955. [PMID: 32547505 PMCID: PMC7272687 DOI: 10.3389/fmicb.2020.00955] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2020] [Accepted: 04/21/2020] [Indexed: 11/13/2022] Open
Abstract
Multidrug resistance (MDR) transporters of the major facilitator superfamily (MFS) were previously believed to drive the extrusion of multiple antimicrobial drugs through the coupling to proton translocation. Here, we present the identification of the first Na+-coupled MFS-MDR transporter, MdrP, which also can achieve H+-coupled drug efflux independently of Na+. Importantly, we propose that MdrP can extrude norfloxacin in a mode of drug/Na+ antiport, which has not yet been reported in any MFS member. On this basis, we further provide the insights into a novel Na+ and H+ coupling mechanism of MFS-MDR transporters, even for all secondary transporters. The most important finding lies in that D223 should mainly act as a key determinant in the Na+ translocation coupled to norfloxacin efflux. Furthermore, our results partially modify the knowledge of the conformational stability-related residues in the motif A of MFS transporters and imply the importance of a new positively charged residue, R361, for the stabilization of outward-facing conformation of MFS transporters. These novel findings positively contribute to the knowledge of MFS-MDR transporters, especially about Na+ and H+ coupling mechanism. This study is based mainly on measurements in intact cells or everted membranes, and a biochemical assay with a reconstituted MdrP protein should be necessary to come to conclusion to be assured.
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Affiliation(s)
- Rui Zhang
- Department of Microbiology and Biotechnology, College of Biological Sciences, Northeast Agricultural University, Harbin, China
| | - Heba Abdel-Motaal
- Department of Microbiology and Biotechnology, College of Biological Sciences, Northeast Agricultural University, Harbin, China
| | - Qiao Zou
- Department of Microbiology and Biotechnology, College of Biological Sciences, Northeast Agricultural University, Harbin, China
| | - Sijia Guo
- Department of Microbiology and Biotechnology, College of Biological Sciences, Northeast Agricultural University, Harbin, China
| | - Xiutao Zheng
- Department of Microbiology and Biotechnology, College of Biological Sciences, Northeast Agricultural University, Harbin, China
| | - Yuting Wang
- Department of Microbiology and Biotechnology, College of Biological Sciences, Northeast Agricultural University, Harbin, China
| | - Zhenglai Zhang
- Department of Microbiology and Biotechnology, College of Biological Sciences, Northeast Agricultural University, Harbin, China
| | - Lin Meng
- Department of Microbiology and Biotechnology, College of Biological Sciences, Northeast Agricultural University, Harbin, China
| | - Tong Xu
- Department of Microbiology and Biotechnology, College of Biological Sciences, Northeast Agricultural University, Harbin, China
| | - Juquan Jiang
- Department of Microbiology and Biotechnology, College of Biological Sciences, Northeast Agricultural University, Harbin, China
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13
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Warnau J, Wöhlert D, Okazaki KI, Yildiz Ö, Gamiz-Hernandez AP, Kaila VRI, Kühlbrandt W, Hummer G. Ion Binding and Selectivity of the Na +/H + Antiporter MjNhaP1 from Experiment and Simulation. J Phys Chem B 2020; 124:336-344. [PMID: 31841344 PMCID: PMC6970264 DOI: 10.1021/acs.jpcb.9b08552] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
![]()
Cells employ membrane-embedded
antiporter proteins to control their
pH, salt concentration, and volume. The large family of cation/proton
antiporters is dominated by Na+/H+ antiporters
that exchange sodium ions against protons, but homologous K+/H+ exchangers have recently been characterized. We show
experimentally that the electroneutral antiporter NhaP1 of Methanocaldococcus jannaschii (MjNhaP1) is highly selective
for Na+ ions. We then characterize the ion selectivity
in both the inward-open and outward-open states of MjNhaP1 using classical
molecular dynamics simulations, free energy calculations, and hybrid
quantum/classical (QM/MM) simulations. We show that MjNhaP1 is highly
selective for binding of Na+ over K+ in the
inward-open state, yet it is only weakly selective in the outward-open
state. These findings are consistent with the function of MjNhaP1
as a sodium-driven deacidifier of the cytosol that maintains a high
cytosolic K+ concentration in environments of high salinity.
By combining experiment and computation, we gain mechanistic insight
into the Na+/H+ transport mechanism and help
elucidate the molecular basis for ion selectivity in cation/proton
exchangers.
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Affiliation(s)
- Judith Warnau
- Department of Theoretical Biophysics , Max Planck Institute of Biophysics , 60438 Frankfurt am Main , Germany.,Department Chemie , Technische Universität München , 85748 Garching , Germany
| | - David Wöhlert
- Department of Structural Biology , Max Planck Institute of Biophysics , 60438 Frankfurt am Main , Germany
| | - Kei-Ichi Okazaki
- Department of Theoretical and Computational Molecular Science, Institute for Molecular Science , National Institutes of Natural Science , Okazaki , 444-8585 , Japan
| | - Özkan Yildiz
- Department of Structural Biology , Max Planck Institute of Biophysics , 60438 Frankfurt am Main , Germany
| | - Ana P Gamiz-Hernandez
- Department Chemie , Technische Universität München , 85748 Garching , Germany.,Department of Biochemistry and Biophysics , Stockholm University , 10691 Stockholm , Sweden
| | - Ville R I Kaila
- Department Chemie , Technische Universität München , 85748 Garching , Germany.,Department of Biochemistry and Biophysics , Stockholm University , 10691 Stockholm , Sweden
| | - Werner Kühlbrandt
- Department of Structural Biology , Max Planck Institute of Biophysics , 60438 Frankfurt am Main , Germany
| | - Gerhard Hummer
- Department of Theoretical Biophysics , Max Planck Institute of Biophysics , 60438 Frankfurt am Main , Germany.,Institute of Biophysics , Goethe University Frankfurt , 60438 Frankfurt am Main , Germany
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14
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Mechanism of the electroneutral sodium/proton antiporter PaNhaP from transition-path shooting. Nat Commun 2019; 10:1742. [PMID: 30988359 PMCID: PMC6465308 DOI: 10.1038/s41467-019-09739-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 03/26/2019] [Indexed: 11/26/2022] Open
Abstract
Na+/H+ antiporters exchange sodium ions and protons on opposite sides of lipid membranes. The electroneutral Na+/H+ antiporter NhaP from archaea Pyrococcus abyssi (PaNhaP) is a functional homolog of the human Na+/H+ exchanger NHE1, which is an important drug target. Here we resolve the Na+ and H+ transport cycle of PaNhaP by transition-path sampling. The resulting molecular dynamics trajectories of repeated ion transport events proceed without bias force, and overcome the enormous time-scale gap between seconds-scale ion exchange and microseconds simulations. The simulations reveal a hydrophobic gate to the extracellular side that opens and closes in response to the transporter domain motion. Weakening the gate by mutagenesis makes the transporter faster, suggesting that the gate balances competing demands of fidelity and efficiency. Transition-path sampling and a committor-based reaction coordinate optimization identify the essential motions and interactions that realize conformational alternation between the two access states in transporter function. Cation-proton antiporters mediate selective ion exchange across cellular membranes to control pH, salt concentration and cell volume. Here the authors present a transition-path sampling method that overcomes the timescale gap between simulations (µs) and transport processes (s), which allows them to resolve the Na+ and H+ transport cycle of the Na+/H+ antiporter NhaP from Pyrococcus abyssi.
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15
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Ribeiro JML, Tsai ST, Pramanik D, Wang Y, Tiwary P. Kinetics of Ligand-Protein Dissociation from All-Atom Simulations: Are We There Yet? Biochemistry 2018; 58:156-165. [PMID: 30547565 DOI: 10.1021/acs.biochem.8b00977] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Large parallel gains in the development of both computational resources and sampling methods have now made it possible to simulate dissociation events in ligand-protein complexes with all-atom resolution. Such encouraging progress, together with the inherent spatiotemporal resolution associated with molecular simulations, has left their use for investigating dissociation processes brimming with potential, both in rational drug design, where it can be an invaluable tool for determining the mechanistic driving forces behind dissociation rate constants, and in force-field development, where it can provide a catalog of transient molecular structures with which to refine force fields. Although much progress has been made in making force fields more accurate, reducing their error for transient structures along a transition path could yet prove to be a critical development helping to make kinetic predictions much more accurate. In what follows, we will provide a state-of-the-art compilation of the enhanced sampling methods based on molecular dynamics (MD) simulations used to investigate the kinetics and mechanisms of ligand-protein dissociation processes. Due to the time scales of such processes being slower than what is accessible using straightforward MD simulations, several ingenious schemes are being devised at a rapid rate to overcome this obstacle. Here we provide an up-to-date compendium of such methods and their achievements and shortcomings in extracting mechanistic insight into ligand-protein dissociation. We conclude with a critical and provocative appraisal attempting to answer the title of this Perspective.
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Affiliation(s)
- João Marcelo Lamim Ribeiro
- Department of Chemistry and Biochemistry , University of Maryland , College Park , Maryland 20742 , United States.,Institute for Physical Science and Technology , University of Maryland , College Park , Maryland 20742 , United States
| | - Sun-Ting Tsai
- Institute for Physical Science and Technology , University of Maryland , College Park , Maryland 20742 , United States.,Department of Physics , University of Maryland , College Park , Maryland 20742 , United States
| | - Debabrata Pramanik
- Department of Chemistry and Biochemistry , University of Maryland , College Park , Maryland 20742 , United States.,Institute for Physical Science and Technology , University of Maryland , College Park , Maryland 20742 , United States
| | - Yihang Wang
- Institute for Physical Science and Technology , University of Maryland , College Park , Maryland 20742 , United States.,Biophysics Program , University of Maryland , College Park , Maryland 20742 , United States
| | - Pratyush Tiwary
- Department of Chemistry and Biochemistry , University of Maryland , College Park , Maryland 20742 , United States.,Institute for Physical Science and Technology , University of Maryland , College Park , Maryland 20742 , United States
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16
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Hollingsworth SA, Dror RO. Molecular Dynamics Simulation for All. Neuron 2018; 99:1129-1143. [PMID: 30236283 PMCID: PMC6209097 DOI: 10.1016/j.neuron.2018.08.011] [Citation(s) in RCA: 993] [Impact Index Per Article: 165.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 07/17/2018] [Accepted: 08/07/2018] [Indexed: 12/12/2022]
Abstract
The impact of molecular dynamics (MD) simulations in molecular biology and drug discovery has expanded dramatically in recent years. These simulations capture the behavior of proteins and other biomolecules in full atomic detail and at very fine temporal resolution. Major improvements in simulation speed, accuracy, and accessibility, together with the proliferation of experimental structural data, have increased the appeal of biomolecular simulation to experimentalists-a trend particularly noticeable in, although certainly not limited to, neuroscience. Simulations have proven valuable in deciphering functional mechanisms of proteins and other biomolecules, in uncovering the structural basis for disease, and in the design and optimization of small molecules, peptides, and proteins. Here we describe, in practical terms, the types of information MD simulations can provide and the ways in which they typically motivate further experimental work.
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Affiliation(s)
- Scott A Hollingsworth
- Department of Computer Science, Stanford University, Stanford, CA 94305, USA; Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University, Stanford, CA 94305, USA; Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA 94305, USA
| | - Ron O Dror
- Department of Computer Science, Stanford University, Stanford, CA 94305, USA; Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA 94305, USA; Department of Structural Biology, Stanford University, Stanford, CA 94305, USA; Institute for Computational and Mathematical Engineering, Stanford University, Stanford, CA 94305, USA.
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17
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Gao X, Gao Q, Bao J. Improving cellulosic ethanol fermentability of Zymomonas mobilis by overexpression of sodium ion tolerance gene ZMO0119. J Biotechnol 2018; 282:32-37. [DOI: 10.1016/j.jbiotec.2018.05.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 05/04/2018] [Accepted: 05/24/2018] [Indexed: 01/31/2023]
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18
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Onoda H, Shoji O, Suzuki K, Sugimoto H, Shiro Y, Watanabe Y. α-Oxidative decarboxylation of fatty acids catalysed by cytochrome P450 peroxygenases yielding shorter-alkyl-chain fatty acids. Catal Sci Technol 2018. [DOI: 10.1039/c7cy02263h] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Shorter-alkyl-chain fatty acids such as tridecanoic acid or lauric acid were produced from myristic acid by CYP152 peroxygenases.
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Affiliation(s)
- Hiroki Onoda
- Department of Chemistry, Graduate School of Science
- Nagoya University
- Nagoya 464-0802
- Japan
| | - Osami Shoji
- Department of Chemistry, Graduate School of Science
- Nagoya University
- Nagoya 464-0802
- Japan
- Core Research for Evolutional Science and Technology (CREST)
| | - Kazuto Suzuki
- Department of Chemistry, Graduate School of Science
- Nagoya University
- Nagoya 464-0802
- Japan
| | - Hiroshi Sugimoto
- Core Research for Evolutional Science and Technology (CREST)
- Japan Science and Technology Agency
- Tokyo
- Japan
- RIKEN SPring-8 Center
| | | | - Yoshihito Watanabe
- Research Center for Materials Science
- Nagoya University
- Nagoya 464-0802
- Japan
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19
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Chu B, Song B, Ji X, Su Y, Wang H, He Y. Fluorescent Silicon Nanorods-Based Ratiometric Sensors for Long-Term and Real-Time Measurements of Intracellular pH in Live Cells. Anal Chem 2017; 89:12152-12159. [PMID: 29050473 DOI: 10.1021/acs.analchem.7b02791] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Long-term and real-time investigation of the dynamic process of pHi changes is critically significant for understanding the related pathogenesis of diseases and the design of intracellular drug delivery systems. Herein, we present a one-step synthetic strategy to construct ratiometric pH sensors, which are made of europium (Eu)-doped one-dimensional silicon nanorods (Eu@SiNRs). The as-prepared Eu@SiNRs have distinct emission maxima peaks at 470 and 620 nm under 405 nm excitation. Of particular note, the fluorescence emission intensity at 470 nm decreases along with the increase of pH, while the one at 620 nm is nearly unaffected by pH changes, making Eu@SiNRs a feasible probe for pH sensing ratiometrically. Moreover, Eu@SiNRs are found to be responsive to a broad pH range (ca. 3-9), biocompatible (e.g., ∼100% of cell viability during 24 h treatment) and photostable (e.g., ∼10% loss of intensity after 40 min continuous UV irradiation). Taking advantages of these merits, we employ Eu@SiNRs for the visualization of the cytoplasmic alkalization process mediated by nigericin in living cells, for around 30 min without interruption, revealing important information for understanding the dynamic process of pHi fluctuations.
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Affiliation(s)
- Binbin Chu
- Laboratory of Nanoscale Biochemical Analysis, Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), and Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC), Soochow University , Suzhou, Jiangsu 215123, China
| | - Bin Song
- Laboratory of Nanoscale Biochemical Analysis, Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), and Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC), Soochow University , Suzhou, Jiangsu 215123, China
| | - Xiaoyuan Ji
- Laboratory of Nanoscale Biochemical Analysis, Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), and Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC), Soochow University , Suzhou, Jiangsu 215123, China
| | - Yuanyuan Su
- Laboratory of Nanoscale Biochemical Analysis, Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), and Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC), Soochow University , Suzhou, Jiangsu 215123, China
| | - Houyu Wang
- Laboratory of Nanoscale Biochemical Analysis, Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), and Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC), Soochow University , Suzhou, Jiangsu 215123, China
| | - Yao He
- Laboratory of Nanoscale Biochemical Analysis, Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), and Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC), Soochow University , Suzhou, Jiangsu 215123, China
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20
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Ligand-induced conformational dynamics of the Escherichia coli Na +/H + antiporter NhaA revealed by hydrogen/deuterium exchange mass spectrometry. Proc Natl Acad Sci U S A 2017; 114:11691-11696. [PMID: 29078272 DOI: 10.1073/pnas.1703422114] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Na+/H+ antiporters comprise a family of membrane proteins evolutionarily conserved in all kingdoms of life and play an essential role in cellular ion homeostasis. The NhaA crystal structure of Escherichia coli has become the paradigm for this class of secondary active transporters. However, structural data are only available at low pH, where NhaA is inactive. Here, we adapted hydrogen/deuterium-exchange mass spectrometry (HDX-MS) to analyze conformational changes in NhaA upon Li+ binding at physiological pH. Our analysis revealed a global conformational change in NhaA with two sets of movements around an immobile binding site. Based on these results, we propose a model for the ion translocation mechanism that explains previously controversial data for this antiporter. Furthermore, these findings contribute to our understanding of related human transporters that have been linked to various diseases.
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21
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Landreh M, Marklund EG, Uzdavinys P, Degiacomi MT, Coincon M, Gault J, Gupta K, Liko I, Benesch JLP, Drew D, Robinson CV. Integrating mass spectrometry with MD simulations reveals the role of lipids in Na +/H + antiporters. Nat Commun 2017; 8:13993. [PMID: 28071645 PMCID: PMC5234078 DOI: 10.1038/ncomms13993] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 11/18/2016] [Indexed: 12/15/2022] Open
Abstract
Na+/H+ antiporters are found in all kingdoms of life and exhibit catalysis rates that are among the fastest of all known secondary-active transporters. Here we combine ion mobility mass spectrometry and molecular dynamics simulations to study the conformational stability and lipid-binding properties of the Na+/H+ exchanger NapA from Thermus thermophilus and compare this to the prototypical antiporter NhaA from Escherichia coli and the human homologue NHA2. We find that NapA and NHA2, but not NhaA, form stable dimers and do not selectively retain membrane lipids. By comparing wild-type NapA with engineered variants, we show that the unfolding of the protein in the gas phase involves the disruption of inter-domain contacts. Lipids around the domain interface protect the native fold in the gas phase by mediating contacts between the mobile protein segments. We speculate that elevator-type antiporters such as NapA, and likely NHA2, use a subset of annular lipids as structural support to facilitate large-scale conformational changes within the membrane.
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Affiliation(s)
- Michael Landreh
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK
| | - Erik G. Marklund
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK
- Department of Chemistry–BMC, Uppsala University, Box 576, Uppsala SE-751 23, Sweden
| | - Povilas Uzdavinys
- Centre for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Stockholm SE-106 91, Sweden
| | - Matteo T. Degiacomi
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK
| | - Mathieu Coincon
- Centre for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Stockholm SE-106 91, Sweden
| | - Joseph Gault
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK
| | - Kallol Gupta
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK
| | - Idlir Liko
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK
| | - Justin L. P. Benesch
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK
| | - David Drew
- Centre for Biomembrane Research, Department of Biochemistry and Biophysics, Stockholm University, Stockholm SE-106 91, Sweden
| | - Carol V. Robinson
- Department of Chemistry, Physical & Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, Oxfordshire OX1 3QZ, UK
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22
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Mechanism of pH-dependent activation of the sodium-proton antiporter NhaA. Nat Commun 2016; 7:12940. [PMID: 27708266 PMCID: PMC5059715 DOI: 10.1038/ncomms12940] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Accepted: 08/17/2016] [Indexed: 11/08/2022] Open
Abstract
Escherichia coli NhaA is a prototype sodium-proton antiporter, which has been extensively characterized by X-ray crystallography, biochemical and biophysical experiments. However, the identities of proton carriers and details of pH-regulated mechanism remain controversial. Here we report constant pH molecular dynamics data, which reveal that NhaA activation involves a net charge switch of a pH sensor at the entrance of the cytoplasmic funnel and opening of a hydrophobic gate at the end of the funnel. The latter is triggered by charging of Asp164, the first proton carrier. The second proton carrier Lys300 forms a salt bridge with Asp163 in the inactive state, and releases a proton when a sodium ion binds Asp163. These data reconcile current models and illustrate the power of state-of-the-art molecular dynamics simulations in providing atomic details of proton-coupled transport across membrane which is challenging to elucidate by experimental techniques. The pH dependence of the activity of Escherichia coli main sodium-proton antiporter NhaA is still not fully understood. Here, the authors use continuous constant pH molecular dynamics simulations to identify NhaA proton carrier residues and elucidate its gating and ion transport processes.
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23
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Chu B, Wang H, Song B, Peng F, Su Y, He Y. Fluorescent and Photostable Silicon Nanoparticles Sensors for Real-Time and Long-Term Intracellular pH Measurement in Live Cells. Anal Chem 2016; 88:9235-42. [PMID: 27539306 DOI: 10.1021/acs.analchem.6b02488] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Fluorescent sensors suitable for dynamic measurement of intracellular pH (pHi) fluctuations should feature the following properties: feeble cytotoxicity, wide-pH range response, and strong fluorescence coupled with good photostability, which are still remaining scanty to date. Herein, by functionalizing fluorescent silicon nanoparticles (SiNPs) with pH-sensitive dopamine (DA) and pH-insensitive rhodamine B isothiocyanate (RBITC), we present the first demonstration of fluorescent SiNPs-based sensors, simultaneously exhibiting minimal toxicity (cell viability of treated cells remains above 95% during 24-h treatment), sensitive fluorescent response to a broad pH range (∼4-10), and bright fluorescence coupled with robust photostability (∼9% loss of fluorescence intensity after 40 min continuous excitation; in contrast, fluorescence of Lyso-tracker is rapidly quenched in 5 min under the same experiment conditions). Taking advantage of these merits, we further employ the resultant fluorescent SiNPs sensors for the detection of lysosomal pH change mediated by nigericin in live HeLa and MCF-7 cells in long-term (e.g., 30 min) manners. Interestingly, two consecutive stages, i.e., alkalization lag phase and logarithmic growth phase, are observed based on recording the whole process of pH change, offering important information for understanding the dynamic process of pHi fluctuations.
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Affiliation(s)
- Binbin Chu
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), and Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC), Soochow University , Suzhou, Jiangsu 215123, China
| | - Houyu Wang
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), and Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC), Soochow University , Suzhou, Jiangsu 215123, China
| | - Bin Song
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), and Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC), Soochow University , Suzhou, Jiangsu 215123, China
| | - Fei Peng
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), and Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC), Soochow University , Suzhou, Jiangsu 215123, China
| | - Yuanyuan Su
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), and Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC), Soochow University , Suzhou, Jiangsu 215123, China
| | - Yao He
- Jiangsu Key Laboratory for Carbon-Based Functional Materials and Devices, Institute of Functional Nano & Soft Materials (FUNSOM), and Collaborative Innovation Center of Suzhou Nano Science and Technology (NANO-CIC), Soochow University , Suzhou, Jiangsu 215123, China
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24
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Flores-Canales JC, Kurnikova M. Targeting electrostatic interactions in accelerated molecular dynamics with application to protein partial unfolding. J Chem Theory Comput 2016; 11:2550-9. [PMID: 26575554 DOI: 10.1021/ct501090y] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Accelerated molecular dynamics (aMD) is a promising sampling method to generate an ensemble of conformations and to explore the free energy landscape of proteins in explicit solvent. Its success resides in its ability to reduce barriers in the dihedral and the total potential energy space. However, aMD simulations of large proteins can generate large fluctuations of the dihedral and total potential energy with little conformational changes in the protein structure. To facilitate wider conformational sampling of large proteins in explicit solvent, we developed a direct intrasolute electrostatic interactions accelerated MD (DISEI-aMD) approach. This method aims to reduce energy barriers within rapidly changing electrostatic interactions between solute atoms at short-range distances. It also results in improved reconstruction quality of the original statistical ensemble of the system. Recently, we characterized a pH-dependent partial unfolding of diphtheria toxin translocation domain (T-domain) using microsecond long MD simulations. In this work, we focus on the study of conformational changes of a low-pH T-domain model in explicit solvent using DISEI-aMD. On the basis of the simulations of the low-pH T-domain model, we show that the proposed sampling method accelerates conformational rearrangement significantly faster than multiple standard aMD simulations and microsecond long conventional MD simulations.
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Affiliation(s)
- Jose C Flores-Canales
- Department of Chemistry, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
| | - Maria Kurnikova
- Department of Chemistry, Carnegie Mellon University , Pittsburgh, Pennsylvania 15213, United States
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25
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Czerny DD, Padmanaban S, Anishkin A, Venema K, Riaz Z, Sze H. Protein architecture and core residues in unwound α-helices provide insights to the transport function of plant AtCHX17. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1983-1998. [PMID: 27179641 DOI: 10.1016/j.bbamem.2016.05.008] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Revised: 04/13/2016] [Accepted: 05/08/2016] [Indexed: 01/27/2023]
Abstract
Using Arabidopsis thaliana AtCHX17 as an example, we combine structural modeling and mutagenesis to provide insights on its protein architecture and transport function which is poorly characterized. This approach is based on the observation that protein structures are significantly more conserved in evolution than linear sequences, and mechanistic similarities among diverse transporters are emerging. Two homology models of AtCHX17 were obtained that show a protein fold similar to known structures of bacterial Na(+)/H(+) antiporters, EcNhaA and TtNapA. The distinct secondary and tertiary structure models highlighted residues at positions potentially important for CHX17 activity. Mutagenesis showed that asparagine-N200 and aspartate-D201 inside transmembrane5 (TM5), and lysine-K355 inside TM10 are critical for AtCHX17 activity. We reveal previously unrecognized threonine-T170 and lysine-K383 as key residues at unwound regions in the middle of TM4 and TM11 α-helices, respectively. Mutation of glutamate-E111 located near the membrane surface inhibited AtCHX17 activity, suggesting a role in pH sensing. The long carboxylic tail of unknown purpose has an alternating β-sheet and α-helix secondary structure that is conserved in prokaryote universal stress proteins. These results support the overall architecture of AtCHX17 and identify D201, N200 and novel residues T170 and K383 at the functional core which likely participates in ion recognition, coordination and/or translocation, similar to characterized cation/H(+) exchangers. The core of AtCHX17 models according to EcNhaA and TtNapA templates faces inward and outward, respectively, which may reflect two conformational states of the alternating access transport mode for proteins belonging to the plant CHX family.
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Affiliation(s)
- Daniel D Czerny
- Department of Cell Biology and Molecular Genetics (DC, SP, ZR, HS), University of Maryland, College Park, MD 20742, USA
| | - Senthilkumar Padmanaban
- Department of Cell Biology and Molecular Genetics (DC, SP, ZR, HS), University of Maryland, College Park, MD 20742, USA
| | - Andriy Anishkin
- Department of Biology, University of Maryland, College Park, MD 20742, USA
| | - Kees Venema
- Dpto de Bioquímica, Biología Celular y Molecular de Plantas, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, c/. Profesor Albareda 1, 18008Granada, Spain
| | - Zoya Riaz
- Department of Cell Biology and Molecular Genetics (DC, SP, ZR, HS), University of Maryland, College Park, MD 20742, USA
| | - Heven Sze
- Department of Cell Biology and Molecular Genetics (DC, SP, ZR, HS), University of Maryland, College Park, MD 20742, USA; Maryland Agricultural Experiment Station, Department of Plant Science and Landscape Architecture (HS), University of Maryland, College Park, MD 20742, USA.
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The Ec-NhaA antiporter switches from antagonistic to synergistic antiport upon a single point mutation. Sci Rep 2016; 6:23339. [PMID: 27021484 PMCID: PMC4810432 DOI: 10.1038/srep23339] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 03/04/2016] [Indexed: 12/14/2022] Open
Abstract
The Na+, Li+/H+ antiporter of Escherichia coli (Ec-NhaA) maintains pH, Na+ homeostasis in enterobacteria. We used isothermal titration calorimetry to perform a detailed thermodynamic analysis of Li+ binding to Ec-NhaA and several of its mutants. We found that, in line with the canonical alternative access mechanistic model of secondary transporters, Li+/H+ binding to the antiporter is antagonistically coupled. Binding of Li+ displaces 2 H+ from the binding site. The process is enthalpically driven, the enthalpic gain just compensating for an entropic loss and the buffer-associated enthalpic changes dominate the overall free-energy change. Li+ binding, H+ release and antiporter activity were all affected to the same extent by mutations in the Li+ binding site (D163E, D163N, D164N, D164E), while D133C changed the H+/Li+ stoichiometry to 4. Most striking, however, was the mutation, A167P, which converted the Ec-NhaA antagonistic binding into synergistic binding which is only known to occur in Cl−/H+ antiporter.
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27
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Crystal structures reveal the molecular basis of ion translocation in sodium/proton antiporters. Nat Struct Mol Biol 2016; 23:248-55. [PMID: 26828964 DOI: 10.1038/nsmb.3164] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Accepted: 12/30/2015] [Indexed: 11/09/2022]
Abstract
To fully understand the transport mechanism of Na(+)/H(+) exchangers, it is necessary to clearly establish the global rearrangements required to facilitate ion translocation. Currently, two different transport models have been proposed. Some reports have suggested that structural isomerization is achieved through large elevator-like rearrangements similar to those seen in the structurally unrelated sodium-coupled glutamate-transporter homolog GltPh. Others have proposed that only small domain movements are required for ion exchange, and a conventional rocking-bundle model has been proposed instead. Here, to resolve these differences, we report atomic-resolution structures of the same Na(+)/H(+) antiporter (NapA from Thermus thermophilus) in both outward- and inward-facing conformations. These data combined with cross-linking, molecular dynamics simulations and isothermal calorimetry suggest that Na(+)/H(+) antiporters provide alternating access to the ion-binding site by using elevator-like structural transitions.
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28
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Sodium-Proton (Na+/H+) Antiporters: Properties and Roles in Health and Disease. Met Ions Life Sci 2016; 16:391-458. [DOI: 10.1007/978-3-319-21756-7_12] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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29
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30
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Abstract
The molecular basis of the function of transporters is a problem of significant importance, and the emerging structural information has not yet been converted to a full understanding of the corresponding function. This work explores the molecular origin of the function of the bacterial Na+/H+ antiporter NhaA by evaluating the energetics of the Na+ and H+ movement and then using the resulting landscape in Monte Carlo simulations that examine two transport models and explore which model can reproduce the relevant experimental results. The simulations reproduce the observed transport features by a relatively simple model that relates the protein structure to its transporting function. Focusing on the two key aspartic acid residues of NhaA, D163 and D164, shows that the fully charged state acts as an Na+ trap and that the fully protonated one poses an energetic barrier that blocks the transport of Na+. By alternating between the former and latter states, mediated by the partially protonated protein, protons, and Na+ can be exchanged across the membrane at 2:1 stoichiometry. Our study provides a numerical validation of the need of large conformational changes for effective transport. Furthermore, we also yield a reasonable explanation for the observation that some mammalian transporters have 1:1 stoichiometry. The present coarse-grained model can provide a general way for exploring the function of transporters on a molecular level.
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31
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Lee C, Yashiro S, Dotson DL, Uzdavinys P, Iwata S, Sansom MSP, von Ballmoos C, Beckstein O, Drew D, Cameron AD. Crystal structure of the sodium-proton antiporter NhaA dimer and new mechanistic insights. ACTA ACUST UNITED AC 2015; 144:529-44. [PMID: 25422503 PMCID: PMC4242812 DOI: 10.1085/jgp.201411219] [Citation(s) in RCA: 67] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A dimeric structure of the sodium–proton antiporter NhaA provides insight into the roles of Asp163 and Lys300 in the transport mechanism. Sodium–proton antiporters rapidly exchange protons and sodium ions across the membrane to regulate intracellular pH, cell volume, and sodium concentration. How ion binding and release is coupled to the conformational changes associated with transport is not clear. Here, we report a crystal form of the prototypical sodium–proton antiporter NhaA from Escherichia coli in which the protein is seen as a dimer. In this new structure, we observe a salt bridge between an essential aspartic acid (Asp163) and a conserved lysine (Lys300). An equivalent salt bridge is present in the homologous transporter NapA, but not in the only other known crystal structure of NhaA, which provides the foundation of most existing structural models of electrogenic sodium–proton antiport. Molecular dynamics simulations show that the stability of the salt bridge is weakened by sodium ions binding to Asp164 and the neighboring Asp163. This suggests that the transport mechanism involves Asp163 switching between forming a salt bridge with Lys300 and interacting with the sodium ion. pKa calculations suggest that Asp163 is highly unlikely to be protonated when involved in the salt bridge. As it has been previously suggested that Asp163 is one of the two residues through which proton transport occurs, these results have clear implications to the current mechanistic models of sodium–proton antiport in NhaA.
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Affiliation(s)
- Chiara Lee
- Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, England, UK
| | - Shoko Yashiro
- Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, England, UK Membrane Protein Laboratory, Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE, England, UK
| | - David L Dotson
- Department of Physics, Arizona State University, Tempe, AZ 85287
| | - Povilas Uzdavinys
- Department of Biochemistry and Biophysics, Centre for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden
| | - So Iwata
- Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, England, UK Membrane Protein Laboratory, Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE, England, UK Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell, Oxford, Didcot, Oxfordshire OX11 0FA, England, UK Japan Science and Technology Agency, ERATO, Human Crystallography Project, Sakyo-ku, Kyoto 606-851, Japan Department of Cell Biology, Graduate School of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Mark S P Sansom
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK
| | - Christoph von Ballmoos
- Department of Biochemistry and Biophysics, Centre for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Oliver Beckstein
- Department of Physics, Arizona State University, Tempe, AZ 85287 Department of Biochemistry, University of Oxford, Oxford OX1 3QU, England, UK
| | - David Drew
- Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, England, UK Department of Biochemistry and Biophysics, Centre for Biomembrane Research, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Alexander D Cameron
- Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, England, UK Membrane Protein Laboratory, Diamond Light Source, Harwell Science and Innovation Campus, Oxfordshire OX11 0DE, England, UK Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell, Oxford, Didcot, Oxfordshire OX11 0FA, England, UK School of Life Sciences, University of Warwick, Coventry CV4 7AL, England, UK
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32
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Kinclova-Zimmermannova O, Falson P, Cmunt D, Sychrova H. A Hydrophobic Filter Confers the Cation Selectivity of Zygosaccharomyces rouxii Plasma-Membrane Na+/H+ Antiporter. J Mol Biol 2015; 427:1681-94. [DOI: 10.1016/j.jmb.2015.02.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Revised: 02/10/2015] [Accepted: 02/11/2015] [Indexed: 10/24/2022]
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33
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Paulino C, Wöhlert D, Kapotova E, Yildiz Ö, Kühlbrandt W. Structure and transport mechanism of the sodium/proton antiporter MjNhaP1. eLife 2014; 3:e03583. [PMID: 25426803 PMCID: PMC4381896 DOI: 10.7554/elife.03583] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2014] [Accepted: 11/14/2014] [Indexed: 11/13/2022] Open
Abstract
Sodium/proton antiporters are essential for sodium and pH homeostasis and play a major role in human health and disease. We determined the structures of the archaeal sodium/proton antiporter MjNhaP1 in two complementary states. The inward-open state was obtained by x-ray crystallography in the presence of sodium at pH 8, where the transporter is highly active. The outward-open state was obtained by electron crystallography without sodium at pH 4, where MjNhaP1 is inactive. Comparison of both structures reveals a 7° tilt of the 6 helix bundle. (22)Na(+) uptake measurements indicate non-cooperative transport with an activity maximum at pH 7.5. We conclude that binding of a Na(+) ion from the outside induces helix movements that close the extracellular cavity, open the cytoplasmic funnel, and result in a ∼5 Å vertical relocation of the ion binding site to release the substrate ion into the cytoplasm.
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Affiliation(s)
- Cristina Paulino
- Department of Structural
Biology, Max Planck Institute of
Biophysics, Frankfurt
am Main, Germany
| | - David Wöhlert
- Department of Structural
Biology, Max Planck Institute of
Biophysics, Frankfurt
am Main, Germany
| | - Ekaterina Kapotova
- Department of Structural
Biology, Max Planck Institute of
Biophysics, Frankfurt
am Main, Germany
| | - Özkan Yildiz
- Department of Structural
Biology, Max Planck Institute of
Biophysics, Frankfurt
am Main, Germany
| | - Werner Kühlbrandt
- Department of Structural
Biology, Max Planck Institute of
Biophysics, Frankfurt
am Main, Germany
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34
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Ion antiport accelerates photosynthetic acclimation in fluctuating light environments. Nat Commun 2014; 5:5439. [PMID: 25451040 PMCID: PMC4243252 DOI: 10.1038/ncomms6439] [Citation(s) in RCA: 156] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2014] [Accepted: 10/01/2014] [Indexed: 12/19/2022] Open
Abstract
Many photosynthetic organisms globally, including crops, forests and algae, must grow in environments where the availability of light energy fluctuates dramatically. How photosynthesis maintains high efficiency despite such fluctuations in its energy source remains poorly understood. Here we show that Arabidopsis thaliana K+ efflux antiporter (KEA3) is critical for high photosynthetic efficiency under fluctuating light. On a shift from dark to low light, or high to low light, kea3 mutants show prolonged dissipation of absorbed light energy as heat. KEA3 localizes to the thylakoid membrane, and allows proton efflux from the thylakoid lumen by proton/potassium antiport. KEA3’s activity accelerates the downregulation of pH-dependent energy dissipation after transitions to low light, leading to faster recovery of high photosystem II quantum efficiency and increased CO2 assimilation. Our results reveal a mechanism that increases the efficiency of photosynthesis under fluctuating light. Plants must respond rapidly to unpredictable variations in light intensity to maximize photosynthetic efficiency. Here Armbruster et al. identify a potassium antiporter that is critical for accelerating proton fluxes across thylakoid membranes and minimizing energy loss in fluctuating light conditions.
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35
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Tan P, Feng Z, Zhang L, Hou T, Li Y. The mechanism of proton translocation in respiratory complex I from molecular dynamics. J Recept Signal Transduct Res 2014; 35:170-9. [PMID: 25055024 DOI: 10.3109/10799893.2014.942464] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Respiratory complex I, the biggest enzyme of respiratory chain, plays a key role in energy production by the mitochondrial respiratory chain and has been implicated in many human neurodegenerative diseases. Recently, the crystal structure of respiratory complex I is reported. We perform 50 ns molecular dynamics simulations on the membrane domain of respiratory complex I under two hypothetical states (oxidized state and reduced state). We find that the density of water molecules in the trans-membrane domain under reduced state is bigger than that under oxidized state. The connecting elements (helix HL and β-hairpins-helix element) fluctuate stronger under reduced state than that under oxidized state, causing more internal water molecules and facilitating the proton conduction. The conformational changes of helix HL and the crucial charged residue Glu in TM5 play key roles in the mechanism of proton translocation. Our results illustrate the dynamic behavior and the potential mechanism of respiratory complex I, which provides the structural basis for drug design of respiratory complex I.
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Affiliation(s)
- Pengli Tan
- Institute of Functional Nano & Soft Materials (FUNSOM) and Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University , Suzhou , China and
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36
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Alves C, Lee BL, Sykes BD, Fliegel L. Structural and Functional Analysis of the Transmembrane Segment Pair VI and VII of the NHE1 Isoform of the Na+/H+ Exchanger. Biochemistry 2014; 53:3658-70. [DOI: 10.1021/bi500392y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Claudia Alves
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
| | - Brian L. Lee
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
| | - Brian D. Sykes
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
| | - Larry Fliegel
- Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
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37
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Schuldiner S. Competition as a way of life for H(+)-coupled antiporters. J Mol Biol 2014; 426:2539-46. [PMID: 24862284 DOI: 10.1016/j.jmb.2014.05.020] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Revised: 05/15/2014] [Accepted: 05/18/2014] [Indexed: 12/13/2022]
Abstract
Antiporters are ubiquitous membrane proteins that catalyze obligatory exchange between two or more substrates across a membrane in opposite directions. Some utilize proton electrochemical gradients generated by primary pumps by coupling the downhill movement of one or more protons to the movement of a substrate. Since the direction of the proton gradient usually favors proton movement toward the cytoplasm, their function results in removal of substrates other than protons from the cytoplasm, either into acidic intracellular compartments or out to the medium. H(+)-coupled antiporters play central roles in living organisms, for example, storage of neurotransmitter and other small molecules, resistance to antibiotics, homeostasis of ionic content and more. Biochemical and structural data support a general mechanism for H(+)-coupled antiporters whereby the substrate and the protons cannot bind simultaneously to the protein. In several cases, it was shown that the binding sites overlap, and therefore, there is a direct competition between the protons and the substrate. In others, the "competition" seems to be indirect and it is most likely achieved by allosteric mechanisms. The pKa of one or more carboxyls in the protein must be tuned appropriately in order to ensure the feasibility of such a mechanism. In this review, I discuss in detail the case of EmrE, a multidrug transporter from Escherichia coli and evaluate the information available for other H(+)-coupled antiporters.
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Affiliation(s)
- Shimon Schuldiner
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel.
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38
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Fischer N, Raunest M, Schmidt TH, Koch DC, Kandt C. Efflux pump-mediated antibiotics resistance: Insights from computational structural biology. Interdiscip Sci 2014; 6:1-12. [DOI: 10.1007/s12539-014-0191-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Revised: 09/03/2013] [Accepted: 11/18/2013] [Indexed: 01/08/2023]
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39
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Abstract
H(+), a most common ion, is involved in very many biological processes. However, most proteins have distinct ranges of pH for function; when the H(+) concentration in the cells is too high or too low, protons turn into very potent stressors to all cells. Therefore, all living cells are strictly dependent on homeostasis mechanisms that regulate their intracellular pH. Na(+)/H(+) antiporters play primary role in pH homeostatic mechanisms both in prokaryotes and eukaryotes. Regulation by pH is a property common to these antiporters. They are equipped with a pH sensor to perceive the pH signal and a pH transducer to transduce the signal into a change in activity. Determining the crystal structure of NhaA, the Na(+)/H(+) antiporter of Escherichia coli have provided the basis for understanding in a realistic rational way the unique regulation of an antiporter by pH and the mechanism of the antiport activity. The physical separation between the pH sensor/transducer and the active site revealed by the structure entailed long-range pH-induced conformational changes for NhaA pH activation. As yet, it is not possible to decide whether the amino acid participating in the pH sensor and the pH transducer overlap or are separated. The pH sensor/transducer is not a single amino acid but rather a cluster of electrostatically interacting residues. Thus, integrating structural, computational, and experimental approaches are essential to reveal how the pH signal is perceived and transduced to activate the pH regulated protein.
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Affiliation(s)
- Etana Padan
- Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem, Israel.
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40
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Functional and structural dynamics of NhaA, a prototype for Na(+) and H(+) antiporters, which are responsible for Na(+) and H(+) homeostasis in cells. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1837:1047-62. [PMID: 24361841 DOI: 10.1016/j.bbabio.2013.12.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Revised: 12/09/2013] [Accepted: 12/13/2013] [Indexed: 01/14/2023]
Abstract
The crystal structure of down-regulated NhaA crystallized at acidic pH4 [21] has provided the first structural insights into the antiport mechanism and pH regulation of a Na(+)/H(+) antiporter [22]. On the basis of the NhaA crystal structure [21] and experimental data (reviewed in [2,22,38] we have suggested that NhaA is organized into two functional regions: (i) a cluster of amino acids responsible for pH regulation (ii) a catalytic region at the middle of the TM IV/XI assembly, with its unique antiparallel unfolded regions that cross each other forming a delicate electrostatic balance in the middle of the membrane. This unique structure contributes to the cation binding site and allows the rapid conformational changes expected for NhaA. Extended chains interrupting helices appear now a common feature for ion binding in transporters. However the NhaA fold is unique and shared by ASBTNM [30] and NapA [29]. Computation [13], electrophysiology [69] combined with biochemistry [33,47] have provided intriguing models for the mechanism of NhaA. However, the conformational changes and the residues involved have not yet been fully identified. Another issue which is still enigma is how energy is transduced "in this 'nano-machine.'" We expect that an integrative approach will reveal the residues that are crucial for NhaA activity and regulation, as well as elucidate the pHand ligand-induced conformational changes and their dynamics. Ultimately, integrative results will shed light on the mechanism of activity and pH regulation of NhaA, a prototype of the CPA2 family of transporters. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference.
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41
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The C-terminal cytoplasmic portion of the NhaP2 cation–proton antiporter from Vibrio cholerae affects its activity and substrate affinity. Mol Cell Biochem 2013; 389:51-8. [DOI: 10.1007/s11010-013-1926-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 12/06/2013] [Indexed: 11/25/2022]
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42
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Rex R, Bill N, Schmidt-Hohagen K, Schomburg D. Swimming in light: a large-scale computational analysis of the metabolism of Dinoroseobacter shibae. PLoS Comput Biol 2013; 9:e1003224. [PMID: 24098096 PMCID: PMC3789786 DOI: 10.1371/journal.pcbi.1003224] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Accepted: 07/31/2013] [Indexed: 01/26/2023] Open
Abstract
The Roseobacter clade is a ubiquitous group of marine α-proteobacteria. To gain insight into the versatile metabolism of this clade, we took a constraint-based approach and created a genome-scale metabolic model (iDsh827) of Dinoroseobacter shibae DFL12T. Our model is the first accounting for the energy demand of motility, the light-driven ATP generation and experimentally determined specific biomass composition. To cover a large variety of environmental conditions, as well as plasmid and single gene knock-out mutants, we simulated 391,560 different physiological states using flux balance analysis. We analyzed our results with regard to energy metabolism, validated them experimentally, and revealed a pronounced metabolic response to the availability of light. Furthermore, we introduced the energy demand of motility as an important parameter in genome-scale metabolic models. The results of our simulations also gave insight into the changing usage of the two degradation routes for dimethylsulfoniopropionate, an abundant compound in the ocean. A side product of dimethylsulfoniopropionate degradation is dimethyl sulfide, which seeds cloud formation and thus enhances the reflection of sunlight. By our exhaustive simulations, we were able to identify single-gene knock-out mutants, which show an increased production of dimethyl sulfide. In addition to the single-gene knock-out simulations we studied the effect of plasmid loss on the metabolism. Moreover, we explored the possible use of a functioning phosphofructokinase for D. shibae. The oceans are home to a large variety of microorganisms, which interact in several ways with world-wide metabolic cycles. A representative of an important group of marine bacteria called the Roseobacter clade is Dinoroseobacter shibae. This organism is known to use a variant of photosynthesis to obtain energy from light. Another feature of D. shibae and many other Roseobacters is the ability to degrade an abundant compound in the ocean called dimethylsulfoniopropionate. Importantly, one degradation pathway of dimethylsulfoniopropionate releases a side product, which affects climate by seeding cloud formation. In this work, we constructed a genome-scale metabolic model of D. shibae and carried out a detailed computational analysis of its metabolism. Our model simulates the light-harvesting capabilities of D. shibae and also accounts for the energy needed to swim. Thanks to our exhaustive simulations we were able to elucidate the effect of light on the growth of D. shibae, to study the consequences of genetic perturbations, and to identify mutants which produce more cloud-seeding compounds. Foremost, our computational results help to understand an important part of the complex processes in the ocean in greater detail. Besides, they can be a valuable guide for future wet-lab experiments.
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Affiliation(s)
- Rene Rex
- Department of Bioinformatics and Biochemistry, Technische Universität Braunschweig, Braunschweig, Germany
| | - Nelli Bill
- Department of Bioinformatics and Biochemistry, Technische Universität Braunschweig, Braunschweig, Germany
| | - Kerstin Schmidt-Hohagen
- Department of Bioinformatics and Biochemistry, Technische Universität Braunschweig, Braunschweig, Germany
| | - Dietmar Schomburg
- Department of Bioinformatics and Biochemistry, Technische Universität Braunschweig, Braunschweig, Germany
- * E-mail:
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Lee C, Kang HJ, von Ballmoos C, Newstead S, Uzdavinys P, Dotson DL, Iwata S, Beckstein O, Cameron AD, Drew D. A two-domain elevator mechanism for sodium/proton antiport. Nature 2013; 501:573-7. [PMID: 23995679 PMCID: PMC3914025 DOI: 10.1038/nature12484] [Citation(s) in RCA: 180] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 07/17/2013] [Indexed: 12/11/2022]
Abstract
Sodium/proton (Na+/H+) antiporters, located at the plasma membrane in every cell, are vital for cell homeostasis1. In humans, their dysfunction has been linked to diseases, such as, hypertension, heart failure and epilepsy and they are well-established drug targets2. The best understood model system for Na+/H+ antiport is NhaA from Escherichia coli1,3, where both EM and crystal structures are available4-6. NhaA is made up of two distinct domains, a Core domain and a Dimerisation domain. In the NhaA crystal structure a cavity is located between the two domains providing access to the ion-binding site from the inward-facing surface of the protein1,4. Like many Na+/H+ antiporters, the activity of NhaA is regulated by pH, only becoming active above pH 6.5, where a conformational change is thought to occur7. To date, the only reported NhaA crystal structure is of the low pH inactivated form4. Here, we describe the active-state structure of a Na+/H+ antiporter, NapA from Thermus thermophilus at 3 Å resolution, solved from crystals grown at pH 7.8. In the NapA structure, the Core and Dimerisation domains are in different positions to those seen in NhaA and a negatively charged cavity has now opened to the outside. The extracellular cavity allows access to a strictly conserved aspartate residue thought to directly coordinate ion-binding1,8,9, a role supported here by molecular dynamics simulations. To alternate access to this ion-binding site, however, requires a surprisingly large rotation of the Core domain, some 20° against the Dimerisation interface. We conclude that despite their fast transport rates of up to 1500 ions/sec3, Na+/H+ antiporters operate by a two-domain rocking bundle model, revealing themes relevant to secondary-active transporters in general.
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Affiliation(s)
- Chiara Lee
- Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, UK
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44
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Structural and functional insights into the cardiac Na+/H+ exchanger. J Mol Cell Cardiol 2013; 61:60-7. [DOI: 10.1016/j.yjmcc.2012.11.019] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2012] [Revised: 11/26/2012] [Accepted: 11/28/2012] [Indexed: 11/19/2022]
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45
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Robinson D. A Polarizable Force-Field for Cholesterol and Sphingomyelin. J Chem Theory Comput 2013; 9:2498-503. [DOI: 10.1021/ct400103e] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- David Robinson
- School of
Chemistry, University of Nottingham, University
Park, Nottingham, NG7 2RD, United Kingdom
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46
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Dror RO, Dirks RM, Grossman JP, Xu H, Shaw DE. Biomolecular simulation: a computational microscope for molecular biology. Annu Rev Biophys 2013; 41:429-52. [PMID: 22577825 DOI: 10.1146/annurev-biophys-042910-155245] [Citation(s) in RCA: 723] [Impact Index Per Article: 65.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Molecular dynamics simulations capture the behavior of biological macromolecules in full atomic detail, but their computational demands, combined with the challenge of appropriately modeling the relevant physics, have historically restricted their length and accuracy. Dramatic recent improvements in achievable simulation speed and the underlying physical models have enabled atomic-level simulations on timescales as long as milliseconds that capture key biochemical processes such as protein folding, drug binding, membrane transport, and the conformational changes critical to protein function. Such simulation may serve as a computational microscope, revealing biomolecular mechanisms at spatial and temporal scales that are difficult to observe experimentally. We describe the rapidly evolving state of the art for atomic-level biomolecular simulation, illustrate the types of biological discoveries that can now be made through simulation, and discuss challenges motivating continued innovation in this field.
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Affiliation(s)
- Ron O Dror
- D. E. Shaw Research, New York, New York 10036, USA.
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Ruggerone P, Vargiu AV, Collu F, Fischer N, Kandt C. Molecular Dynamics Computer Simulations of Multidrug RND Efflux Pumps. Comput Struct Biotechnol J 2013; 5:e201302008. [PMID: 24688701 PMCID: PMC3962194 DOI: 10.5936/csbj.201302008] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 01/31/2013] [Accepted: 02/04/2013] [Indexed: 01/13/2023] Open
Abstract
Over-expression of multidrug efflux pumps of the Resistance Nodulation Division (RND) protein super family counts among the main causes for microbial resistance against pharmaceuticals. Understanding the molecular basis of this process is one of the major challenges of modern biomedical research, involving a broad range of experimental and computational techniques. Here we review the current state of RND transporter investigation employing molecular dynamics simulations providing conformational samples of transporter components to obtain insights into the functional mechanism underlying efflux pump-mediated antibiotics resistance in Escherichia coli and Pseudomonas aeruginosa.
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Affiliation(s)
- Paolo Ruggerone
- Department of Physics, University of Cagliari, Cittadella Universitaria S.P. Monserrato-Sestu Km 0.700, 09042 Monserrato (CA), Cagliari, Italy ; CNR-IOM, Unità SLACS, S.P. Monserrato-Sestu Km 0.700, I-09042 Monserrato (CA), Italy
| | - Attilio V Vargiu
- Department of Physics, University of Cagliari, Cittadella Universitaria S.P. Monserrato-Sestu Km 0.700, 09042 Monserrato (CA), Cagliari, Italy ; CNR-IOM, Unità SLACS, S.P. Monserrato-Sestu Km 0.700, I-09042 Monserrato (CA), Italy
| | - Francesca Collu
- Departement fu r Chemie und Biochemie, Universita t Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
| | - Nadine Fischer
- Computational Structural Biology, Department of Life Science Informatics B-IT, Life & Medical Sciences Institute, University of Bonn, Dahlmannstr. 2, 53113 Bonn, Germany
| | - Christian Kandt
- Computational Structural Biology, Department of Life Science Informatics B-IT, Life & Medical Sciences Institute, University of Bonn, Dahlmannstr. 2, 53113 Bonn, Germany
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48
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Structures of a Na+-coupled, substrate-bound MATE multidrug transporter. Proc Natl Acad Sci U S A 2013; 110:2099-104. [PMID: 23341609 DOI: 10.1073/pnas.1219901110] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Multidrug transporters belonging to the multidrug and toxic compound extrusion (MATE) family expel dissimilar lipophilic and cationic drugs across cell membranes by dissipating a preexisting Na(+) or H(+) gradient. Despite its clinical relevance, the transport mechanism of MATE proteins remains poorly understood, largely owing to a lack of structural information on the substrate-bound transporter. Here we report crystal structures of a Na(+)-coupled MATE transporter NorM from Neisseria gonorrheae in complexes with three distinct translocation substrates (ethidium, rhodamine 6G, and tetraphenylphosphonium), as well as Cs(+) (a Na(+) congener), all captured in extracellular-facing and drug-bound states. The structures revealed a multidrug-binding cavity festooned with four negatively charged amino acids and surprisingly limited hydrophobic moieties, in stark contrast to the general belief that aromatic amino acids play a prominent role in multidrug recognition. Furthermore, we discovered an uncommon cation-π interaction in the Na(+)-binding site located outside the drug-binding cavity and validated the biological relevance of both the substrate- and cation-binding sites by conducting drug resistance and transport assays. Additionally, we uncovered potential rearrangement of at least two transmembrane helices upon Na(+)-induced drug export. Based on our structural and functional analyses, we suggest that Na(+) triggers multidrug extrusion by inducing protein conformational changes rather than by directly competing for the substrate-binding amino acids. This scenario is distinct from the canonical antiport mechanism, in which both substrate and counterion compete for a shared binding site in the transporter. Collectively, our findings provide an important step toward a detailed and mechanistic understanding of multidrug transport.
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Enkavi G, Li J, Mahinthichaichan P, Wen PC, Huang Z, Shaikh SA, Tajkhorshid E. Simulation studies of the mechanism of membrane transporters. Methods Mol Biol 2013; 924:361-405. [PMID: 23034756 DOI: 10.1007/978-1-62703-017-5_14] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Membrane transporters facilitate active transport of their specific substrates, often against their electrochemical gradients across the membrane, through coupling the process to various sources of cellular energy, for example, ATP binding and hydrolysis in primary transporters, and pre-established electrochemical gradient of molecular species other than the substrate in the case of secondary transporters. In order to provide efficient energy-coupling mechanisms, membrane transporters have evolved into molecular machines in which stepwise binding, translocation, and transformation of various molecular species are closely coupled to protein conformational changes that take the transporter from one functional state to another during the transport cycle. Furthermore, in order to prevent the formation of leaky states and to be able to pump the substrate against its electrochemical gradient, all membrane transporters use the widely-accepted "alternating access mechanism," which ensures that the substrate is only accessible from one side of the membrane at a given time, but relies on complex and usually global protein conformational changes that differ for each family of membrane transporters. Describing the protein conformational changes of different natures and magnitudes is therefore at the heart of mechanistic studies of membrane transporters. Here, using a number of membrane transporters from diverse families, we present common protocols used in setting up and performing molecular dynamics simulations of membrane transporters and in analyzing the results, in order to characterize relevant motions of the system. The emphasis will be on highlighting how optimal design of molecular dynamics simulations combined with mechanistically oriented analysis can shed light onto key functionally relevant protein conformational changes in this family of membrane proteins.
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Affiliation(s)
- Giray Enkavi
- Department of Biochemistry, Center for Biophysics and Computational Biology, College of Medicine, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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50
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Maffeo C, Bhattacharya S, Yoo J, Wells D, Aksimentiev A. Modeling and simulation of ion channels. Chem Rev 2012; 112:6250-84. [PMID: 23035940 PMCID: PMC3633640 DOI: 10.1021/cr3002609] [Citation(s) in RCA: 148] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Christopher Maffeo
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - Swati Bhattacharya
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - Jejoong Yoo
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - David Wells
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
| | - Aleksei Aksimentiev
- Department of Physics, University of Illinois, 1110 W. Green St., Urbana, IL
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