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Kell DB. A protet-based, protonic charge transfer model of energy coupling in oxidative and photosynthetic phosphorylation. Adv Microb Physiol 2021; 78:1-177. [PMID: 34147184 DOI: 10.1016/bs.ampbs.2021.01.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Textbooks of biochemistry will explain that the otherwise endergonic reactions of ATP synthesis can be driven by the exergonic reactions of respiratory electron transport, and that these two half-reactions are catalyzed by protein complexes embedded in the same, closed membrane. These views are correct. The textbooks also state that, according to the chemiosmotic coupling hypothesis, a (or the) kinetically and thermodynamically competent intermediate linking the two half-reactions is the electrochemical difference of protons that is in equilibrium with that between the two bulk phases that the coupling membrane serves to separate. This gradient consists of a membrane potential term Δψ and a pH gradient term ΔpH, and is known colloquially as the protonmotive force or pmf. Artificial imposition of a pmf can drive phosphorylation, but only if the pmf exceeds some 150-170mV; to achieve in vivo rates the imposed pmf must reach 200mV. The key question then is 'does the pmf generated by electron transport exceed 200mV, or even 170mV?' The possibly surprising answer, from a great many kinds of experiment and sources of evidence, including direct measurements with microelectrodes, indicates it that it does not. Observable pH changes driven by electron transport are real, and they control various processes; however, compensating ion movements restrict the Δψ component to low values. A protet-based model, that I outline here, can account for all the necessary observations, including all of those inconsistent with chemiosmotic coupling, and provides for a variety of testable hypotheses by which it might be refined.
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Affiliation(s)
- Douglas B Kell
- Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative, Biology, University of Liverpool, Liverpool, United Kingdom; The Novo Nordisk Foundation Center for Biosustainability, Technical University of Denmark, Lyngby, Denmark.
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2
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Rasafar N, Barzegar A, Mehdizadeh Aghdam E. Design and development of high affinity dual anticancer peptide-inhibitors against p53-MDM2/X interaction. Life Sci 2020; 245:117358. [PMID: 32001262 DOI: 10.1016/j.lfs.2020.117358] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Revised: 01/22/2020] [Accepted: 01/24/2020] [Indexed: 12/16/2022]
Abstract
AIMS Inhibition of P53-MDM2/X interaction is known as an effective cancer therapy strategy. In this regard, pDI peptide was introduced previously with the potential of targeting MDM2. In this research, the large-scale peptide mutation screening was used to achieve the best sequence of pDI with the highest affinity for inhibition activity against MDM2/X. MAIN METHODS Three mutant peptides of pDI as dual inhibitor peptides including single mutations of pDIm/4W, pDIm/11M and double mutations of pDIdm/4W11M were presented with the high affinities to inhibit both MDM2/X. The selected mutants were then evaluated comprehensively to confirm their ability as potent MDM2/X inhibitors, using a theoretical simulation approach. KEY FINDINGS MD simulations analyses confirmed their dual inhibition potential against both MDM2/X interactions with p53 protein. The developed pDIm and mainly pDIdm peptides showed stable conformations over the simulation time with conserved secondary structure and effective interaction with MDM2/X by physical binding such as hydrogen bonding. Besides, umbrella sampling free energy calculation indicated higher binding energy, ΔGbinding, of pDIm-MDM2/X and pDIdm-MDM2/X compared to pDI-MDM2/X. SIGNIFICANCE The optimized and improved mutant pDI, pDIdm, with more effective ΔGbinding values of -30 and -25 kcal/mol to MDMX and MDM2, respectively, is recommended as a promising anticancer agent and suitable candidate for experimental evaluations.
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Affiliation(s)
- Nasim Rasafar
- Research Institute of Bioscience and Biotechnology, University of Tabriz, Tabriz, Iran
| | - Abolfazl Barzegar
- Research Institute of Bioscience and Biotechnology, University of Tabriz, Tabriz, Iran.
| | - Elnaz Mehdizadeh Aghdam
- Molecular Medicine Research Center, Biomedicine Institute, Tabriz University of Medical Sciences, Tabriz, Iran; Department of Pharmaceutical Biotechnology, Faculty of Pharmacy, Tabriz University of Medical Sciences, Tabriz, Iran.
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Kaya D, Kjellerup BV, Chourey K, Hettich RL, Taggart DM, Löffler FE. Impact of Fixed Nitrogen Availability on Dehalococcoides mccartyi Reductive Dechlorination Activity. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:14548-14558. [PMID: 31693350 DOI: 10.1021/acs.est.9b04463] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Biostimulation to promote reductive dechlorination is widely practiced, but the value of adding an exogenous nitrogen (N) source (e.g., NH4+) during treatment is unclear. This study investigates the effect of NH4+ availability on organohalide-respiring Dehalococcoides mccartyi (Dhc) growth and reductive dechlorination in enrichment cultures derived from groundwater (PW4) and river sediment (TC) impacted with chlorinated ethenes. In PW4 cultures, the addition of NH4+ increased cis-1,2-dichloroethene (cDCE)-to-ethene dechlorination rates about 5-fold (20.6 ± 1.6 versus 3.8 ± 0.5 μM Cl- d-1), and the total number of Dhc 16S rRNA gene copies were about 43-fold higher in incubations with NH4+ ((1.8 ± 0.9) × 108 mL-1) compared to incubations without NH4+ ((4.1 ± 0.8) × 107 mL-1). In TC cultures, NH4+ also stimulated cDCE-to-ethene dechlorination and Dhc growth. Quantitative polymerase chain reaction (qPCR) revealed that Cornell-type Dhc capable of N2 fixation dominated PW4 cultures without NH4+, but their relative abundance decreased in cultures with NH4+ amendment (i.e., 99 versus 54% of total Dhc). Pinellas-type Dhc incapable of N2 fixation were responsible for cDCE dechlorination in TC cultures, and diazotrophic community members met their fixed N requirement in the medium without NH4+. Responses to NH4+ were apparent at the community level, and N2-fixing bacterial populations increased in incubations without NH4+. Quantitative assessment of Dhc nitrogenase genes, transcripts, and proteomics data linked Cornell-type Dhc nifD and nifK expression with fixed N limitation. NH4+ additions also demonstrated positive effects on Dhc in situ dechlorination activity in the vicinity of well PW4. These findings demonstrate that biostimulation with NH4+ can enhance Dhc reductive dechlorination rates; however, a "do nothing" approach that relies on indigenous diazotrophs can achieve similar dechlorination end points and avoids the potential for stalled dechlorination due to inhibitory levels of NH4+ or transformation products (i.e., nitrous oxide).
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Affiliation(s)
- Devrim Kaya
- Biosciences Division and ⊥Chemical Sciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
- Department of Civil and Environmental Engineering , University of Maryland College Park , College Park , Maryland 20742 , United States
| | - Birthe V Kjellerup
- Department of Civil and Environmental Engineering , University of Maryland College Park , College Park , Maryland 20742 , United States
| | | | | | - Dora M Taggart
- Microbial Insights, Inc. , Knoxville , Tennessee 37932 , United States
| | - Frank E Löffler
- Biosciences Division and ⊥Chemical Sciences Division , Oak Ridge National Laboratory , Oak Ridge , Tennessee 37831 , United States
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4
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A pore-occluding phenylalanine gate prevents ion slippage through plant ammonium transporters. Sci Rep 2019; 9:16765. [PMID: 31727964 PMCID: PMC6856177 DOI: 10.1038/s41598-019-53333-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 10/31/2019] [Indexed: 01/08/2023] Open
Abstract
Throughout all kingdoms of life, highly conserved transport proteins mediate the passage of ammonium across membranes. These transporters share a high homology and a common pore structure. Whether NH3, NH4+ or NH3 + H+ is the molecularly transported substrate, still remains unclear for distinct proteins. High-resolution protein structures of several ammonium transporters suggested two conserved pore domains, an external NH4+ recruitment site and a pore-occluding twin phenylalanine gate, to take over a crucial role in substrate determination and selectivity. Here, we show that while the external recruitment site seems essential for AtAMT1;2 function, single mutants of the double phenylalanine gate were not reduced in their ammonium transport capacity. Despite an unchanged ammonium transport rate, a single mutant of the inner phenylalanine showed reduced N-isotope selection that was proposed to be associated with ammonium deprotonation during transport. Even though ammonium might pass the mutant AMT pore in the ionic form, the transporter still excluded potassium ions from being transported. Our results, highlight the importance of the twin phenylalanine gate in blocking uncontrolled ammonium ion flux.
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Chen J, Wang J, Zhang Q, Chen K, Zhu W. Probing Origin of Binding Difference of inhibitors to MDM2 and MDMX by Polarizable Molecular Dynamics Simulation and QM/MM-GBSA Calculation. Sci Rep 2015; 5:17421. [PMID: 26616018 PMCID: PMC4663504 DOI: 10.1038/srep17421] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Accepted: 10/29/2015] [Indexed: 12/13/2022] Open
Abstract
Binding abilities of current inhibitors to MDMX are weaker than to MDM2. Polarizable molecular dynamics simulations (MD) followed by Quantum mechanics/molecular mechanics generalized Born surface area (QM//MM-GBSA) calculations were performed to investigate the binding difference of inhibitors to MDM2 and MDMX. The predicted binding free energies not only agree well with the experimental results, but also show that the decrease in van der Walls interactions of inhibitors with MDMX relative to MDM2 is a main factor of weaker bindings of inhibitors to MDMX. The analyses of dihedral angles based on MD trajectories suggest that the closed conformation formed by the residues M53 and Y99 in MDMX leads to a potential steric clash with inhibitors and prevents inhibitors from arriving in the deep of MDMX binding cleft, which reduces the van der Waals contacts of inhibitors with M53, V92, P95 and L98. The calculated results using the residue-based free energy decomposition method further prove that the interaction strength of inhibitors with M53, V92, P95 and L98 from MDMX are obviously reduced compared to MDM2. We expect that this study can provide significant theoretical guidance for designs of potent dual inhibitors to block the p53-MDM2/MDMX interactions.
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Affiliation(s)
- Jianzhong Chen
- School of Science, Shandong Jiaotong University, Jinan, 250014, China
| | - Jinan Wang
- Discovery and Design Center, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203, China
| | - Qinggang Zhang
- College of Physics and Electronics, Shandong Normal University, Jinan, 250014, China
| | - Kaixian Chen
- Discovery and Design Center, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203, China
| | - Weiliang Zhu
- Discovery and Design Center, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zuchongzhi Road, Shanghai, 201203, China
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7
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Shi S, Zhang S, Zhang Q. Probing Difference in Binding Modes of Inhibitors to MDMX by Molecular Dynamics Simulations and Different Free Energy Methods. PLoS One 2015; 10:e0141409. [PMID: 26513747 PMCID: PMC4625964 DOI: 10.1371/journal.pone.0141409] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2015] [Accepted: 10/08/2015] [Indexed: 01/20/2023] Open
Abstract
The p53-MDMX interaction has attracted extensive attention of anti-cancer drug development in recent years. This current work adopted molecular dynamics (MD) simulations and cross-correlation analysis to investigate conformation changes of MDMX caused by inhibitor bindings. The obtained information indicates that the binding cleft of MDMX undergoes a large conformational change and the dynamic behavior of residues obviously change by the presence of different structural inhibitors. Two different methods of binding free energy predictions were employed to carry out a comparable insight into binding mechanisms of four inhibitors PMI, pDI, WK23 and WW8 to MDMX. The data show that the main factor controlling the inhibitor bindings to MDMX arises from van der Waals interactions. The binding free energies were further divided into contribution of each residue and the derived information gives a conclusion that the hydrophobic interactions, such as CH-CH, CH-π and π-π interactions, are responsible for the inhibitor associations with MDMX.
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Affiliation(s)
- Shuhua Shi
- School of Science, Shandong Jianzhu University, Jinan, China
- * E-mail: ;
| | - Shaolong Zhang
- College of Physics and Electronics, Shandong Normal University, Jinan, China
| | - Qinggang Zhang
- College of Physics and Electronics, Shandong Normal University, Jinan, China
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Cheng W, Liang Z, Wang W, Yi C, Li H, Zhang S, Zhang Q. Insight into binding modes of p53 and inhibitors to MDM2 based on molecular dynamic simulations and principal component analysis. Mol Phys 2015. [DOI: 10.1080/00268976.2015.1087598] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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9
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Chen J, Wang X, Zhu T, Zhang Q, Zhang JZH. A Comparative Insight into Amprenavir Resistance of Mutations V32I, G48V, I50V, I54V, and I84V in HIV-1 Protease Based on Thermodynamic Integration and MM-PBSA Methods. J Chem Inf Model 2015; 55:1903-13. [DOI: 10.1021/acs.jcim.5b00173] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Jianzhong Chen
- School
of Science, Shandong Jiaotong University, Jinan 250357 China
| | - Xingyu Wang
- NYU−ECNU
Center for Computational Chemistry at NYU Shanghai, Shanghai 200062, China
| | - Tong Zhu
- State
Key Laboratory of Precision Spectroscopy, Institute of Theoretical
and Computational Science, East China Normal University, Shanghai 200062, China
| | - Qinggang Zhang
- Collage
of Physics and Electronic Science, Shandong Normal University, Jinan 250014, China
| | - John Z. H. Zhang
- NYU−ECNU
Center for Computational Chemistry at NYU Shanghai, Shanghai 200062, China
- State
Key Laboratory of Precision Spectroscopy, Institute of Theoretical
and Computational Science, East China Normal University, Shanghai 200062, China
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Chen J, Wang J, Zhang Q, Chen K, Zhu W. A comparative study of trypsin specificity based on QM/MM molecular dynamics simulation and QM/MM GBSA calculation. J Biomol Struct Dyn 2015; 33:2606-18. [PMID: 25562613 DOI: 10.1080/07391102.2014.1003146] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Hydrogen bonding and polar interactions play a key role in identification of protein-inhibitor binding specificity. Quantum mechanics/molecular mechanics molecular dynamics (QM/MM MD) simulations combined with DFT and semi-empirical Hamiltonian (AM1d, RM1, PM3, and PM6) methods were performed to study the hydrogen bonding and polar interactions of two inhibitors BEN and BEN1 with trypsin. The results show that the accuracy of treating the hydrogen bonding and polar interactions using QM/MM MD simulation of PM6 can reach the one obtained by the DFT QM/MM MD simulation. Quantum mechanics/molecular mechanics generalized Born surface area (QM/MM-GBSA) method was applied to calculate binding affinities of inhibitors to trypsin and the results suggest that the accuracy of binding affinity prediction can be significantly affected by the accurate treatment of the hydrogen bonding and polar interactions. In addition, the calculated results also reveal the binding specificity of trypsin: (1) the amidinium groups of two inhibitors generate favorable salt bridge interaction with Asp189 and form hydrogen bonding interactions with Ser190 and Gly214, (2) the phenyl of inhibitors can produce favorable van der Waals interactions with the residues His58, Cys191, Gln192, Trp211, Gly212, and Cys215. This systematic and comparative study can provide guidance for the choice of QM/MM MD methods and the designs of new potent inhibitors targeting trypsin.
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Affiliation(s)
- Jianzhong Chen
- a School of Science , Shandong Jiaotong University , Jinan , 250014 , China
| | - Jinan Wang
- b Discovery and Design Center , CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zuchongzhi Road, Shanghai , 201203 , China
| | - Qinggang Zhang
- c College of Physics and Electronics , Shandong Normal University , Jinan , 250014 , China
| | - Kaixian Chen
- b Discovery and Design Center , CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zuchongzhi Road, Shanghai , 201203 , China
| | - Weiliang Zhu
- b Discovery and Design Center , CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences , 555 Zuchongzhi Road, Shanghai , 201203 , China
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12
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Chen J, Liang Z, Wang W, Yi C, Zhang S, Zhang Q. Revealing origin of decrease in potency of darunavir and amprenavir against HIV-2 relative to HIV-1 protease by molecular dynamics simulations. Sci Rep 2014; 4:6872. [PMID: 25362963 PMCID: PMC4217091 DOI: 10.1038/srep06872] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 10/13/2014] [Indexed: 12/30/2022] Open
Abstract
Clinical inhibitors Darunavir (DRV) and Amprenavir (APV) are less effective on HIV-2 protease (PR2) than on HIV-1 protease (PR1). To identify molecular basis associated with the lower inhibition, molecular dynamics (MD) simulations and molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) calculations were performed to investigate the effectiveness of the PR1 inhibitors DRV and APV against PR1/PR2. The rank of predicted binding free energies agrees with the experimental determined one. Moreover, our results show that two inhibitors bind less strongly to PR2 than to PR1, again in agreement with the experimental findings. The decrease in binding free energies for PR2 relative to PR1 is found to arise from the reduction of the van der Waals interactions induced by the structural adjustment of the triple mutant V32I, I47V and V82I. This result is further supported by the difference between the van der Waals interactions of inhibitors with each residue in PR2 and in PR1. The results from the principle component analysis suggest that inhibitor binding tends to make the flaps of PR2 close and the one of PR1 open. We expect that this study can theoretically provide significant guidance and dynamics information for the design of potent dual inhibitors targeting PR1/PR2.
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Affiliation(s)
- Jianzhong Chen
- School of Science, Shandong Jiaotong University, Jinan 250357, China
| | - Zhiqiang Liang
- School of Science, Shandong Jiaotong University, Jinan 250357, China
| | - Wei Wang
- School of Science, Shandong Jiaotong University, Jinan 250357, China
| | - Changhong Yi
- School of Science, Shandong Jiaotong University, Jinan 250357, China
| | - Shaolong Zhang
- College of Physics and Electronics, Shandong Normal University, Jinan, 250014, China
| | - Qinggang Zhang
- College of Physics and Electronics, Shandong Normal University, Jinan, 250014, China
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Shi S, Zhang S, Zhang Q. Insight into the interaction mechanism of inhibitors P4 and WK23 with MDM2 based on molecular dynamics simulation and different free energy methods. COMPUT THEOR CHEM 2014. [DOI: 10.1016/j.comptc.2014.07.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Chen J, Wang J, Zhu W. Binding modes of three inhibitors 8CA, F8A and I4A to A-FABP studied based on molecular dynamics simulation. PLoS One 2014; 9:e99862. [PMID: 24918907 PMCID: PMC4053400 DOI: 10.1371/journal.pone.0099862] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2014] [Accepted: 05/16/2014] [Indexed: 12/21/2022] Open
Abstract
Adipocyte fatty-acid binding protein (A-FABP) is an important target of drug designs treating some diseases related to lipid-mediated biology. Molecular dynamics (MD) simulations coupled with solvated interaction energy method (SIE) were carried out to study the binding modes of three inhibitors 8CA, F8A and I4A to A-FABP. The rank of our predicted binding affinities is in accordance with experimental data. The results show that the substitution in the position 5 of N-benzyl and the seven-membered ring of N-benzyl-indole carboxylic acids strengthen the I4A binding, while the substitution in the position 2 of N-benzyl weakens the F8A binding. Computational alanine scanning and dynamics analyses were performed and the results suggest that the polar interactions of the positively charged residue R126 with the three inhibitors provide a significant contribution to inhibitor bindings. This polar interaction induces the disappearance of the correlated motion of the C terminus of A-FABP relative to the N terminus and favors the stability of the binding complex. This study is helpful for the rational design of potent inhibitors within the fields of metabolic disease, inflammation and atherosclerosis.
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Affiliation(s)
- Jianzhong Chen
- School of Science, Shandong Jiaotong University, Jinan, China
- * E-mail: (JC); (WZ)
| | - Jinan Wang
- Discovery and Design Center, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
| | - Weiliang Zhu
- Discovery and Design Center, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
- * E-mail: (JC); (WZ)
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Graça FA, Gonçalves DAP, Silveira WA, Lira EC, Chaves VE, Zanon NM, Garófalo MAR, Kettelhut IC, Navegantes LCC. Epinephrine depletion exacerbates the fasting-induced protein breakdown in fast-twitch skeletal muscles. Am J Physiol Endocrinol Metab 2013; 305:E1483-94. [PMID: 24169047 DOI: 10.1152/ajpendo.00267.2013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The physiological role of epinephrine in the regulation of skeletal muscle protein metabolism under fasting is unknown. We examined the effects of plasma epinephrine depletion, induced by adrenodemedullation (ADMX), on muscle protein metabolism in fed and 2-day-fasted rats. In fed rats, ADMX for 10 days reduced muscle mass, the cross-sectional area of extensor digitorum longus (EDL) muscle fibers, and the phosphorylation levels of Akt. In addition, ADMX led to a compensatory increase in muscle sympathetic activity, as estimated by the rate of norepinephrine turnover; this increase was accompanied by high rates of muscle protein synthesis. In fasted rats, ADMX exacerbated fasting-induced proteolysis in EDL but did not affect the low rates of protein synthesis. Accordingly, ADMX activated lysosomal proteolysis and further increased the activity of the ubiquitin (Ub)-proteasome system (UPS). Moreover, expression of the atrophy-related Ub ligases atrogin-1 and MuRF1 and the autophagy-related genes LC3b and GABARAPl1 were upregulated in EDL muscles from ADMX-fasted rats compared with sham-fasted rats, and ADMX reduced cAMP levels and increased fasting-induced Akt dephosphorylation. Unlike that observed for EDL muscles, soleus muscle proteolysis and Akt phosphorylation levels were not affected by ADMX. In isolated EDL, epinephrine reduced the basal UPS activity and suppressed overall proteolysis and atrogin-1 and MuRF1 induction following fasting. These data suggest that epinephrine released from the adrenal medulla inhibits fasting-induced protein breakdown in fast-twitch skeletal muscles, and these antiproteolytic effects on the UPS and lysosomal system are apparently mediated through a cAMP-Akt-dependent pathway, which suppresses ubiquitination and autophagy.
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Affiliation(s)
- Flávia A Graça
- Department of Physiology, Ribeirão Preto Medical School, University of São Paulo, São Paulo, Brazil
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van Heeswijk WC, Westerhoff HV, Boogerd FC. Nitrogen assimilation in Escherichia coli: putting molecular data into a systems perspective. Microbiol Mol Biol Rev 2013; 77:628-95. [PMID: 24296575 PMCID: PMC3973380 DOI: 10.1128/mmbr.00025-13] [Citation(s) in RCA: 159] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
We present a comprehensive overview of the hierarchical network of intracellular processes revolving around central nitrogen metabolism in Escherichia coli. The hierarchy intertwines transport, metabolism, signaling leading to posttranslational modification, and transcription. The protein components of the network include an ammonium transporter (AmtB), a glutamine transporter (GlnHPQ), two ammonium assimilation pathways (glutamine synthetase [GS]-glutamate synthase [glutamine 2-oxoglutarate amidotransferase {GOGAT}] and glutamate dehydrogenase [GDH]), the two bifunctional enzymes adenylyl transferase/adenylyl-removing enzyme (ATase) and uridylyl transferase/uridylyl-removing enzyme (UTase), the two trimeric signal transduction proteins (GlnB and GlnK), the two-component regulatory system composed of the histidine protein kinase nitrogen regulator II (NRII) and the response nitrogen regulator I (NRI), three global transcriptional regulators called nitrogen assimilation control (Nac) protein, leucine-responsive regulatory protein (Lrp), and cyclic AMP (cAMP) receptor protein (Crp), the glutaminases, and the nitrogen-phosphotransferase system. First, the structural and molecular knowledge on these proteins is reviewed. Thereafter, the activities of the components as they engage together in transport, metabolism, signal transduction, and transcription and their regulation are discussed. Next, old and new molecular data and physiological data are put into a common perspective on integral cellular functioning, especially with the aim of resolving counterintuitive or paradoxical processes featured in nitrogen assimilation. Finally, we articulate what still remains to be discovered and what general lessons can be learned from the vast amounts of data that are available now.
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Chen J, Wang J, Zhu W, Li G. A computational analysis of binding modes and conformation changes of MDM2 induced by p53 and inhibitor bindings. J Comput Aided Mol Des 2013; 27:965-74. [PMID: 24264557 DOI: 10.1007/s10822-013-9693-z] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2013] [Accepted: 11/17/2013] [Indexed: 10/26/2022]
Abstract
Molecular dynamics (MD) simulations followed by principal component analysis were performed to study the conformational change of MDM2 induced by p53 and two inhibitor (P4 and MI63a) bindings. The results show that the hydrophobic cleft of MDM2 is very flexible and adaptive to different structural binding partners. The cleft tends to become wider and more stable as MDM2 binds to the three binding partners, while unbound MDM2 shows a narrower and pretty flexible cleft, which agrees with recent experimental data and theoretical studies. It was also found that the binding of P4 and p53 stabilizes the motion of the loop L2 linking the helix α2 and β strand (β3), but the presence of MI63a makes the motion of L2 disordered. In addition, the binding free energies of the three partners to MDM2 were calculated using molecular mechanics generalized Born surface area to explain the binding modes of these three partners to MDM2. This study will be helpful not only for better understanding the functional, concerted motion of MDM2, but also for the rational design of potent anticancer drugs targeting the p53-MDM2 interaction.
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Affiliation(s)
- Jianzhong Chen
- School of Science, Shandong Jiaotong University, Jinan, 250014, China,
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Wang J, Fulford T, Shao Q, Javelle A, Yang H, Zhu W, Merrick M. Ammonium transport proteins with changes in one of the conserved pore histidines have different performance in ammonia and methylamine conduction. PLoS One 2013; 8:e62745. [PMID: 23667517 PMCID: PMC3647058 DOI: 10.1371/journal.pone.0062745] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2012] [Accepted: 03/25/2013] [Indexed: 01/02/2023] Open
Abstract
Two conserved histidine residues are located near the mid-point of the conduction channel of ammonium transport proteins. The role of these histidines in ammonia and methylamine transport was evaluated by using a combination of in vivo studies, molecular dynamics (MD) simulation, and potential of mean force (PMF) calculations. Our in vivo results showed that a single change of either of the conserved histidines to alanine leads to the failure to transport methylamine but still facilitates good growth on ammonia, whereas double histidine variants completely lose their ability to transport both methylamine and ammonia. Molecular dynamics simulations indicated the molecular basis of the in vivo observations. They clearly showed that a single histidine variant (H168A or H318A) of AmtB confines the rather hydrophobic methylamine more strongly than ammonia around the mutated sites, resulting in dysfunction in conducting the former but not the latter molecule. PMF calculations further revealed that the single histidine variants form a potential energy well of up to 6 kcal/mol for methylamine, impairing conduction of this substrate. Unlike the single histidine variants, the double histidine variant, H168A/H318A, of AmtB was found to lose its unidirectional property of transporting both ammonia and methylamine. This could be attributed to a greatly increased frequency of opening of the entrance gate formed by F215 and F107, in this variant compared to wild-type, with a resultant lowering of the energy barrier for substrate to return to the periplasm.
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Affiliation(s)
- Jinan Wang
- Drug Discovery and Design Center, CAS Key Laboratory of Receptor Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China
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Ullmann RT, Andrade SLA, Ullmann GM. Thermodynamics of transport through the ammonium transporter Amt-1 investigated with free energy calculations. J Phys Chem B 2012; 116:9690-703. [PMID: 22804733 DOI: 10.1021/jp305440f] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Amt-1 from Archaeoglobus fulgidus (AfAmt-1) belongs to the Amt/Rh family of ammonium/ammonia transporting membrane proteins. The transport mode and the precise microscopic permeation mechanism utilized by these proteins are intensely debated. Open questions concern the identity of the transported substrate (ammonia and/or ammonium) and whether the transport is passive or active. To address these questions, we studied the overall thermodynamics of the different transport modes as a function of the environmental conditions. Then, we investigated the thermodynamics of the underlying microscopic transport mechanisms with free energy calculations within a continuum electrostatics model. The formalism developed for this purpose is of general utility in the calculation of binding free energies for ligands with multiple protonation forms or other binding forms. The results of our calculations are compared to the available experimental and theoretical data on Amt/Rh proteins and discussed in light of the current knowledge on the physiological conditions experienced by microorganisms and plants. We found that microscopic models of electroneutral and electrogenic transport modes are in principle thermodynamically viable. However, only the electrogenic variants have a net thermodynamic driving force under the physiological conditions experienced by microorganisms and plants. Thus, the transport mechanism of AfAmt-1 is most likely electrogenic.
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Affiliation(s)
- R Thomas Ullmann
- Structural Biology/Bioinformatics, University of Bayreuth, Universitätsstrasse 30, BGI, 95447 Bayreuth, Germany.
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