1
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Pozarycki C, Seaton KM, C Vincent E, Novak Sanders C, Nuñez N, Castillo M, Ingall E, Klempay B, Pontefract A, Fisher LA, Paris ER, Buessecker S, Alansson NB, Carr CE, Doran PT, Bowman JS, Schmidt BE, Stockton AM. Biosignature Molecules Accumulate and Persist in Evaporitic Brines: Implications for Planetary Exploration. ASTROBIOLOGY 2024; 24:795-812. [PMID: 39159437 DOI: 10.1089/ast.2023.0122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/21/2024]
Abstract
The abundance of potentially habitable hypersaline environments in our solar system compels us to understand the impacts of high-salt matrices and brine dynamics on biosignature detection efforts. We identified and quantified organic compounds in brines from South Bay Salt Works (SBSW), where evapoconcentration of ocean water enables exploration of the impact of NaCl- and MgCl2-dominated brines on the detection of potential biosignature molecules. In SBSW, organic biosignature abundance and distribution are likely influenced by evapoconcentration, osmolyte accumulation, and preservation effects. Bioluminescence assays show that adenosine triphosphate (ATP) concentrations are higher in NaCl-rich, low water activity (aw) samples (<0.85) from SBSW. This is consistent with the accumulation and preservation of ATP at low aw as described in past laboratory studies. The water-soluble small organic molecule inventory was determined by using microchip capillary electrophoresis paired with high-resolution mass spectrometry (µCE-HRMS). We analyzed the relative distribution of proteinogenic amino acids with a recently developed quantitative method using CE-separation and laser-induced fluorescence (LIF) detection of amino acids in hypersaline brines. Salinity trends for dissolved free amino acids were consistent with amino acid residue abundance determined from the proteome of the microbial community predicted from metagenomic data. This highlights a tangible connection up and down the "-omics" ladder across changing geochemical conditions. The detection of water-soluble organic compounds, specifically proteinogenic amino acids at high abundance (>7 mM) in concentrated brines, demonstrates that potential organic biomarkers accumulate at hypersaline sites and suggests the possibility of long-term preservation. The detection of such molecules in high abundance when using diverse analytical tools appropriate for spacecraft suggests that life detection within hypersaline environments, such as evaporates on Mars and the surface or subsurface brines of ocean world Europa, is plausible and argues such environments should be a high priority for future exploration. Key Words: Salts-Analytical chemistry-Amino acids-Biosignatures-Capillary electrophoresis-Preservation. Astrobiology 24, 795-812.
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Affiliation(s)
- Chad Pozarycki
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Kenneth M Seaton
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Emily C Vincent
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Carlie Novak Sanders
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Nickie Nuñez
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Mariah Castillo
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Ellery Ingall
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Benjamin Klempay
- Scripps Institution of Oceanography, University of California San Diego, San Diego, California, USA
| | | | - Luke A Fisher
- Scripps Institution of Oceanography, University of California San Diego, San Diego, California, USA
| | - Emily R Paris
- Department of Earth System Science, Stanford University, Stanford, California, USA
| | - Steffen Buessecker
- Department of Earth System Science, Stanford University, Stanford, California, USA
| | - Nikolas B Alansson
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Christopher E Carr
- School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
- Daniel Guggenheim School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Peter T Doran
- Geology and Geophysics, Louisiana State University, Baton Rouge, Louisiana, USA
| | - Jeff S Bowman
- Scripps Institution of Oceanography, University of California San Diego, San Diego, California, USA
| | - Britney E Schmidt
- Departments of Astronomy and Earth & Atmospheric Sciences, Cornell University, Ithaca, New York, USA
| | - Amanda M Stockton
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
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2
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Wang Y, Wu J, Zsolnay V, Pollard TD, Voth GA. Mechanism of Phosphate Release from Actin Filaments. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2023.08.03.551904. [PMID: 37577500 PMCID: PMC10418243 DOI: 10.1101/2023.08.03.551904] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
After ATP-actin monomers assemble filaments, the ATP's γ-phosphate is hydrolyzed within seconds and dissociates over minutes. We used all-atom molecular dynamics simulations to sample the release of phosphate from filaments and study residues that gate release. Dissociation of phosphate from Mg2+ is rate limiting and associated with an energy barrier of 20 kcal/mol, consistent with experimental rates of phosphate release. Phosphate then diffuses in an internal cavity toward a gate formed by R177 suggested in prior computational studies and cryo-EM structures. The gate is closed when R177 hydrogen bonds with N111 and is open when R177 forms a salt bridge with D179. Most of the time interactions of R177 with other residues occludes the phosphate release pathway. Machine learning analysis reveals that the occluding interactions fluctuate rapidly, underscoring the secondary role of backdoor gate opening in Pi release, in contrast with the previous hypothesis that gate opening is the primary event.
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Affiliation(s)
- Yihang Wang
- Department of Chemistry, Chicago Center for Theoretical Chemistry, Institute for Biophysical Dynamics and James Frank Institute, University of Chicago, Chicago, IL
| | - Jiangbo Wu
- Department of Chemistry, Chicago Center for Theoretical Chemistry, Institute for Biophysical Dynamics and James Frank Institute, University of Chicago, Chicago, IL
| | - Vilmos Zsolnay
- Graduate Program in Biophysical Sciences, University of Chicago, Chicago, IL
| | - Thomas D. Pollard
- Department of Molecular Cellular and Developmental Biology, Yale University, New Haven, CT
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT
- Department of Cell Biology, Yale University, New Haven, CT
| | - Gregory A. Voth
- Department of Chemistry, Chicago Center for Theoretical Chemistry, Institute for Biophysical Dynamics and James Frank Institute, University of Chicago, Chicago, IL
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3
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Szántó JK, Dietschreit JCB, Shein M, Schütz AK, Ochsenfeld C. Systematic QM/MM Study for Predicting 31P NMR Chemical Shifts of Adenosine Nucleotides in Solution and Stages of ATP Hydrolysis in a Protein Environment. J Chem Theory Comput 2024; 20:2433-2444. [PMID: 38497488 DOI: 10.1021/acs.jctc.3c01280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/19/2024]
Abstract
NMR (nuclear magnetic resonance) spectroscopy allows for important atomistic insights into the structure and dynamics of biological macromolecules; however, reliable assignments of experimental spectra are often difficult. Herein, quantum mechanical/molecular mechanical (QM/MM) calculations can provide crucial support. A major problem for the simulations is that experimental NMR signals are time-averaged over much longer time scales, and since computed chemical shifts are highly sensitive to local changes in the electronic and structural environment, sufficiently large averages over representative structural ensembles are essential. This entails high computational demands for reliable simulations. For NMR measurements in biological systems, a nucleus of major interest is 31P since it is both highly present (e.g., in nucleic acids) and easily observable. The focus of our present study is to develop a robust and computationally cost-efficient framework for simulating 31P NMR chemical shifts of nucleotides. We apply this scheme to study the different stages of the ATP hydrolysis reaction catalyzed by p97. Our methodology is based on MM molecular dynamics (MM-MD) sampling, followed by QM/MM structure optimizations and NMR calculations. Overall, our study is one of the most comprehensive QM-based 31P studies in a protein environment and the first to provide computed NMR chemical shifts for multiple nucleotide states in a protein environment. This study sheds light on a process that is challenging to probe experimentally and aims to bridge the gap between measured and calculated NMR spectroscopic properties.
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Affiliation(s)
- Judit Katalin Szántó
- Chair of Theoretical Chemistry, Department of Chemistry, University of Munich (LMU), Butenandtstr. 7, D-81377 München, Germany
| | - Johannes C B Dietschreit
- Chair of Theoretical Chemistry, Department of Chemistry, University of Munich (LMU), Butenandtstr. 7, D-81377 München, Germany
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Mikhail Shein
- Department of Chemistry, University of Munich (LMU), Butenandtstr. 5-13, D-81377 München, Germany
| | - Anne K Schütz
- Department of Chemistry, University of Munich (LMU), Butenandtstr. 5-13, D-81377 München, Germany
| | - Christian Ochsenfeld
- Chair of Theoretical Chemistry, Department of Chemistry, University of Munich (LMU), Butenandtstr. 7, D-81377 München, Germany
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, D-70569 Stuttgart, Germany
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4
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Bursch M, Mewes J, Hansen A, Grimme S. Best-Practice DFT Protocols for Basic Molecular Computational Chemistry. Angew Chem Int Ed Engl 2022; 61:e202205735. [PMID: 36103607 PMCID: PMC9826355 DOI: 10.1002/anie.202205735] [Citation(s) in RCA: 153] [Impact Index Per Article: 76.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2022] [Indexed: 01/11/2023]
Abstract
Nowadays, many chemical investigations are supported by routine calculations of molecular structures, reaction energies, barrier heights, and spectroscopic properties. The lion's share of these quantum-chemical calculations applies density functional theory (DFT) evaluated in atomic-orbital basis sets. This work provides best-practice guidance on the numerous methodological and technical aspects of DFT calculations in three parts: Firstly, we set the stage and introduce a step-by-step decision tree to choose a computational protocol that models the experiment as closely as possible. Secondly, we present a recommendation matrix to guide the choice of functional and basis set depending on the task at hand. A particular focus is on achieving an optimal balance between accuracy, robustness, and efficiency through multi-level approaches. Finally, we discuss selected representative examples to illustrate the recommended protocols and the effect of methodological choices.
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Affiliation(s)
- Markus Bursch
- Max-Planck-Institut für KohlenforschungKaiser-Wilhelm-Platz 145470Mülheim an der RuhrGermany
| | - Jan‐Michael Mewes
- Mulliken Center for Theoretical ChemistryInstitut für Physikalische und Theoretische ChemieUniversität BonnBeringstraße 453115BonnGermany
| | - Andreas Hansen
- Mulliken Center for Theoretical ChemistryInstitut für Physikalische und Theoretische ChemieUniversität BonnBeringstraße 453115BonnGermany
| | - Stefan Grimme
- Mulliken Center for Theoretical ChemistryInstitut für Physikalische und Theoretische ChemieUniversität BonnBeringstraße 453115BonnGermany
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5
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Bursch M, Mewes J, Hansen A, Grimme S. Best‐Practice DFT Protocols for Basic Molecular Computational Chemistry**. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202205735] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Markus Bursch
- Max-Planck-Institut für Kohlenforschung Kaiser-Wilhelm-Platz 1 45470 Mülheim an der Ruhr Germany
| | - Jan‐Michael Mewes
- Mulliken Center for Theoretical Chemistry Institut für Physikalische und Theoretische Chemie Universität Bonn Beringstraße 4 53115 Bonn Germany
| | - Andreas Hansen
- Mulliken Center for Theoretical Chemistry Institut für Physikalische und Theoretische Chemie Universität Bonn Beringstraße 4 53115 Bonn Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry Institut für Physikalische und Theoretische Chemie Universität Bonn Beringstraße 4 53115 Bonn Germany
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6
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Simm GN, Türtscher PL, Reiher M. Systematic microsolvation approach with a cluster-continuum scheme and conformational sampling. J Comput Chem 2020; 41:1144-1155. [PMID: 32027384 DOI: 10.1002/jcc.26161] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2019] [Revised: 01/11/2020] [Accepted: 01/16/2020] [Indexed: 12/12/2022]
Abstract
Solvation is a notoriously difficult and nagging problem for the rigorous theoretical description of chemistry in the liquid phase. Successes and failures of various approaches ranging from implicit solvation modeling through dielectric continuum embedding and microsolvated quantum chemical modeling to explicit molecular dynamics highlight this situation. Here, we focus on quantum chemical microsolvation and discuss an explicit conformational sampling ansatz to make this approach systematic. For this purpose, we introduce an algorithm for rolling and automated microsolvation of solutes. Our protocol takes conformational sampling and rearrangements in the solvent shell into account. Its reliability is assessed by monitoring the evolution of the spread and average of the observables of interest.
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Affiliation(s)
- Gregor N Simm
- Laboratory of Physical Chemistry, ETH Zürich, Zürich, Switzerland
| | - Paul L Türtscher
- Laboratory of Physical Chemistry, ETH Zürich, Zürich, Switzerland
| | - Markus Reiher
- Laboratory of Physical Chemistry, ETH Zürich, Zürich, Switzerland
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7
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Calixto AR, Moreira C, Pabis A, Kötting C, Gerwert K, Rudack T, Kamerlin SCL. GTP Hydrolysis Without an Active Site Base: A Unifying Mechanism for Ras and Related GTPases. J Am Chem Soc 2019; 141:10684-10701. [PMID: 31199130 DOI: 10.1021/jacs.9b03193] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
GTP hydrolysis is a biologically crucial reaction, being involved in regulating almost all cellular processes. As a result, the enzymes that catalyze this reaction are among the most important drug targets. Despite their vital importance and decades of substantial research effort, the fundamental mechanism of enzyme-catalyzed GTP hydrolysis by GTPases remains highly controversial. Specifically, how do these regulatory proteins hydrolyze GTP without an obvious general base in the active site to activate the water molecule for nucleophilic attack? To answer this question, we perform empirical valence bond simulations of GTPase-catalyzed GTP hydrolysis, comparing solvent- and substrate-assisted pathways in three distinct GTPases, Ras, Rab, and the Gαi subunit of a heterotrimeric G-protein, both in the presence and in the absence of the corresponding GTPase activating proteins. Our results demonstrate that a general base is not needed in the active site, as the preferred mechanism for GTP hydrolysis is a conserved solvent-assisted pathway. This pathway involves the rate-limiting nucleophilic attack of a water molecule, leading to a short-lived intermediate that tautomerizes to form H2PO4- and GDP as the final products. Our fundamental biochemical insight into the enzymatic regulation of GTP hydrolysis not only resolves a decades-old mechanistic controversy but also has high relevance for drug discovery efforts. That is, revisiting the role of oncogenic mutants with respect to our mechanistic findings would pave the way for a new starting point to discover drugs for (so far) "undruggable" GTPases like Ras.
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Affiliation(s)
- Ana R Calixto
- Department of Chemistry-BMC , Uppsala University , Box 576, S-751 23 Uppsala , Sweden
| | - Cátia Moreira
- Department of Chemistry-BMC , Uppsala University , Box 576, S-751 23 Uppsala , Sweden
| | - Anna Pabis
- Department of Cell and Molecular Biology , Uppsala University , BMC Box 596, S-751 24 , Uppsala , Sweden
| | - Carsten Kötting
- Department of Biophysics , Ruhr University Bochum , 44801 Bochum , Germany
| | - Klaus Gerwert
- Department of Biophysics , Ruhr University Bochum , 44801 Bochum , Germany
| | - Till Rudack
- Department of Biophysics , Ruhr University Bochum , 44801 Bochum , Germany
| | - Shina C L Kamerlin
- Department of Chemistry-BMC , Uppsala University , Box 576, S-751 23 Uppsala , Sweden
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8
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Daru J, Bakó I, Stirling A, Pápai I. Mechanism of Heterolytic Hydrogen Splitting by Frustrated Lewis Pairs: Comparison of Static and Dynamic Models. ACS Catal 2019. [DOI: 10.1021/acscatal.9b01137] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- János Daru
- Research Center for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, Budapest H-1117, Hungary
| | - Imre Bakó
- Research Center for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, Budapest H-1117, Hungary
| | - András Stirling
- Research Center for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, Budapest H-1117, Hungary
| | - Imre Pápai
- Research Center for Natural Sciences, Hungarian Academy of Sciences, Magyar tudósok körútja 2, Budapest H-1117, Hungary
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9
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Prieß M, Göddeke H, Groenhof G, Schäfer LV. Molecular Mechanism of ATP Hydrolysis in an ABC Transporter. ACS CENTRAL SCIENCE 2018; 4:1334-1343. [PMID: 30410971 PMCID: PMC6202651 DOI: 10.1021/acscentsci.8b00369] [Citation(s) in RCA: 57] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Indexed: 05/28/2023]
Abstract
Hydrolysis of nucleoside triphosphate (NTP) plays a key role for the function of many biomolecular systems. However, the chemistry of the catalytic reaction in terms of an atomic-level understanding of the structural, dynamic, and free energy changes associated with it often remains unknown. Here, we report the molecular mechanism of adenosine triphosphate (ATP) hydrolysis in the ATP-binding cassette (ABC) transporter BtuCD-F. Free energy profiles obtained from hybrid quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations show that the hydrolysis reaction proceeds in a stepwise manner. First, nucleophilic attack of an activated lytic water molecule at the ATP γ-phosphate yields ADP + HPO4 2- as intermediate product. A conserved glutamate that is located very close to the γ-phosphate transiently accepts a proton and thus acts as catalytic base. In the second step, the proton is transferred back from the catalytic base to the γ-phosphate, yielding ADP + H2PO4 -. These two chemical reaction steps are followed by rearrangements of the hydrogen bond network and the coordination of the Mg2+ ion. The rate constant estimated from the computed free energy barriers is in very good agreement with experiments. The overall free energy change of the reaction is close to zero, suggesting that phosphate bond cleavage itself does not provide a power stroke for conformational changes. Instead, ATP binding is essential for tight dimerization of the nucleotide-binding domains and the transition of the transmembrane domains from inward- to outward-facing, whereas ATP hydrolysis resets the conformational cycle. The mechanism is likely relevant for all ABC transporters and might have implications also for other NTPases, as many residues involved in nucleotide binding and hydrolysis are strictly conserved.
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Affiliation(s)
- Marten Prieß
- Theoretical
Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, D-44780 Bochum, Germany
| | - Hendrik Göddeke
- Theoretical
Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, D-44780 Bochum, Germany
| | - Gerrit Groenhof
- Department
of Chemistry and Nanoscience Center, University
of Jyväskylä, P.O. Box
35, FI-40014 Jyväskylä, Finland
| | - Lars V. Schäfer
- Theoretical
Chemistry, Faculty of Chemistry and Biochemistry, Ruhr-University Bochum, D-44780 Bochum, Germany
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10
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Pérez-Villa A, Saitta AM, Georgelin T, Lambert JF, Guyot F, Maurel MC, Pietrucci F. Synthesis of RNA Nucleotides in Plausible Prebiotic Conditions from ab Initio Computer Simulations. J Phys Chem Lett 2018; 9:4981-4987. [PMID: 30107125 DOI: 10.1021/acs.jpclett.8b02077] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Understanding the mechanism of spontaneous formation of ribonucleotides under realistic prebiotic conditions is a key open issue of origins-of-life research. In cells, de novo and salvage nucleotide enzymatic synthesis combines 5-phospho-α-d-ribose-1-diphosphate (α-PRPP) and nucleobases. Interestingly, these reactants are also known as prebiotically plausible compounds. Combining ab initio molecular dynamics simulations with recently developed reaction exploration and enhanced sampling methods, we show that nucleobases and α-PRPP should spontaneously combine, under mild hydrothermal conditions, with an exothermic reaction and a facile mechanism, forming both purine and pyrimidine ribonucleotides. Surprisingly, this mechanism is very similar to the biological one and yields ribonucleotides with the same anomeric carbon chirality as in biological systems. Mass spectrometry experiments performed on solutions of adenine and PRPP in similar conditions support the formation of AMP. These results suggest that natural selection might have optimized, through enzymes, a pre-existing ribonucleotide formation mechanism, carrying it forward to modern life forms.
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Affiliation(s)
- Andrea Pérez-Villa
- Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, IRD, Institut de Minéralogie, de Physique des Matriaux et de Cosmochimie, IMPMC, F-75005 Paris , France
| | - A Marco Saitta
- Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, IRD, Institut de Minéralogie, de Physique des Matriaux et de Cosmochimie, IMPMC, F-75005 Paris , France
| | - Thomas Georgelin
- Sorbonne Université, CNRS UMR 7197, Laboratoire de Réactivité de Surface, LRS, F-75005 Paris , France
- Centre de Biophysique Moléculaire, CNRS UPR 4301, F-45071 Orléans , France
| | - Jean-François Lambert
- Sorbonne Université, CNRS UMR 7197, Laboratoire de Réactivité de Surface, LRS, F-75005 Paris , France
| | - François Guyot
- Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, IRD, Institut de Minéralogie, de Physique des Matriaux et de Cosmochimie, IMPMC, F-75005 Paris , France
| | - Marie-Christine Maurel
- Sorbonne Université, Muséum National d'Histoire Naturelle, CNRS MNHN UMR 7205, Institut de Systématique, Evolution, Biodiversité, ISyEB, F-75005 Paris , France
| | - Fabio Pietrucci
- Sorbonne Université, Muséum National d'Histoire Naturelle, UMR CNRS 7590, IRD, Institut de Minéralogie, de Physique des Matriaux et de Cosmochimie, IMPMC, F-75005 Paris , France
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11
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Fatima T, Rani S, Fischer S, Efferth T, Kiani FA. The hydrolysis of 6-phosphogluconolactone in the second step of pentose phosphate pathway occurs via a two-water mechanism. Biophys Chem 2018; 240:98-106. [PMID: 30014892 DOI: 10.1016/j.bpc.2018.06.002] [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: 05/06/2018] [Revised: 06/08/2018] [Accepted: 06/09/2018] [Indexed: 11/28/2022]
Abstract
Hydrolysis reaction marks the basis of life yet the mechanism of this crucial biochemical reaction is not completely understood. We recently reported the mechanisms of hydrolysis of nucleoside triphosphate and phosphate monoester. These two reactions hydrolyze P-O-P and P-O-C linkages, respectively. Here, we present the mechanism of hydrolysis of δ-6-phosphogluconolactone, which is an important precursor in the second step of the pentose phosphate pathway. Its hydrolysis requires the cleavage of C-O-C linkage and its mechanism is hitherto unknown. We report three mechanisms of hydrolysis of δ-6-phosphogluconolactone based on density functional computations. In the energetically most favorable mechanism, two water molecules participate in the hydrolysis reaction and the mechanism is sequential, i.e., activation of the attacking water molecule (OH bond breaking) precedes that of the cleavage of the CO bond of the C-O-C linkage. The rate-limiting energy barrier of this mechanism is comparable to the reported experimental free energy barrier. This mechanism has similarities with the mechanism of triphosphate hydrolysis and that of hydrolytic cleavage of DNA in EcoRV enzyme. This two-water sequential hydrolysis mechanism could be the unified mechanism required for the hydrolysis of other hydrolysable species in living cells.
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Affiliation(s)
- Tabeer Fatima
- Research Center for Modeling and Simulation (RCMS), National University of Sciences and Technology (NUST), Sector H-12, 44000 Islamabad, Pakistan; Department of Biotechnology, University of Sialkot, 51310 Sialkot, Pakistan
| | - Sadaf Rani
- Research Center for Modeling and Simulation (RCMS), National University of Sciences and Technology (NUST), Sector H-12, 44000 Islamabad, Pakistan
| | - Stefan Fischer
- Interdisciplinary Center for Scientific Computing, The University of Heidelberg, D-69120 Heidelberg, Germany
| | - Thomas Efferth
- Department of Pharmaceutical Biology, Johannes Gutenberg University, Staudinger Weg 5, 55128 Mainz, Germany
| | - Farooq Ahmad Kiani
- Research Center for Modeling and Simulation (RCMS), National University of Sciences and Technology (NUST), Sector H-12, 44000 Islamabad, Pakistan; Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany Street, 02118 Boston, MA, United States.
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12
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Jeong K, Shim J, Chung WY, Kye YS, Kim D. Diisopropyl fluorophosphate (DFP) degradation activity using transition metal-dipicolylamine complexes. Appl Organomet Chem 2018. [DOI: 10.1002/aoc.4383] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Keunhong Jeong
- Department of Chemistry; Korea Military Academy; Seoul 01805 South Korea
| | - Joongmoo Shim
- Department of Chemistry; Korea Military Academy; Seoul 01805 South Korea
| | - Woo Young Chung
- Department of Chemistry; Korea Military Academy; Seoul 01805 South Korea
| | - Young Sik Kye
- Department of Chemistry; Korea Military Academy; Seoul 01805 South Korea
| | - Dongwook Kim
- Department of Chemistry; Korea Military Academy; Seoul 01805 South Korea
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13
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Davidson RB, Hendrix J, Geiss BJ, McCullagh M. Allostery in the dengue virus NS3 helicase: Insights into the NTPase cycle from molecular simulations. PLoS Comput Biol 2018; 14:e1006103. [PMID: 29659571 PMCID: PMC5919694 DOI: 10.1371/journal.pcbi.1006103] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2017] [Revised: 04/26/2018] [Accepted: 03/22/2018] [Indexed: 12/29/2022] Open
Abstract
The C-terminus domain of non-structural 3 (NS3) protein of the Flaviviridae viruses (e.g. HCV, dengue, West Nile, Zika) is a nucleotide triphosphatase (NTPase) -dependent superfamily 2 (SF2) helicase that unwinds double-stranded RNA while translocating along the nucleic polymer. Due to these functions, NS3 is an important target for antiviral development yet the biophysics of this enzyme are poorly understood. Microsecond-long molecular dynamic simulations of the dengue NS3 helicase domain are reported from which allosteric effects of RNA and NTPase substrates are observed. The presence of a bound single-stranded RNA catalytically enhances the phosphate hydrolysis reaction by affecting the dynamics and positioning of waters within the hydrolysis active site. Coupled with results from the simulations, electronic structure calculations of the reaction are used to quantify this enhancement to be a 150-fold increase, in qualitative agreement with the experimental enhancement factor of 10–100. Additionally, protein-RNA interactions exhibit NTPase substrate-induced allostery, where the presence of a nucleotide (e.g. ATP or ADP) structurally perturbs residues in direct contact with the phosphodiester backbone of the RNA. Residue-residue network analyses highlight pathways of short ranged interactions that connect the two active sites. These analyses identify motif V as a highly connected region of protein structure through which energy released from either active site is hypothesized to move, thereby inducing the observed allosteric effects. These results lay the foundation for the design of novel allosteric inhibitors of NS3. Non-structural protein 3 (NS3) is a Flaviviridae (e.g. Hepatitis C, dengue, and Zika viruses) helicase that unwinds double stranded RNA while translocating along the nucleic polymer during viral genome replication. As a member of superfamily 2 (SF2) helicases, NS3 utilizes the free energy of nucleotide triphosphate (NTP) binding, hydrolysis, and product unbinding to perform its functions. While much is known about SF2 helicases, the pathways and mechanisms through which free energy is transduced between the NTP hydrolysis active site and RNA binding cleft remains elusive. Here we present a multiscale computational study to characterize the allosteric effects induced by the RNA and NTPase substrates (ATP, ADP, and Pi) as well as the pathways of short-range, residue-residue interactions that connect the two active sites. Results from this body of molecular dynamics simulations and electronic structure calculations are highlighted in context to the NTPase enzymatic cycle, allowing for development of testable hypotheses for validation of these simulations. Our insights, therefore, provide novel details about the biophysics of NS3 and guide the next generation of experimental studies.
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Affiliation(s)
- Russell B. Davidson
- Department of Chemistry, Colorado State University, Fort Collins, Colorado, United States of America
| | - Josie Hendrix
- Department of Chemistry, Colorado State University, Fort Collins, Colorado, United States of America
| | - Brian J. Geiss
- Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, United States of America
- School of Biomedical Engineering, Colorado State University, Fort Collins, Colorado, United States of America
| | - Martin McCullagh
- Department of Chemistry, Colorado State University, Fort Collins, Colorado, United States of America
- * E-mail:
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14
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Boereboom JM, Fleurat-Lessard P, Bulo RE. Explicit Solvation Matters: Performance of QM/MM Solvation Models in Nucleophilic Addition. J Chem Theory Comput 2018; 14:1841-1852. [PMID: 29438621 PMCID: PMC6023263 DOI: 10.1021/acs.jctc.7b01206] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
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Nucleophilic
addition onto a carbonyl moiety is strongly affected
by solvent, and correctly simulating this solvent effect is often
beyond the capability of single-scale quantum mechanical (QM) models.
This work explores multiscale approaches for the description of the
reversible and highly solvent-sensitive nucleophilic N|···C=O
bond formation in an Me2N–(CH2)3–CH=O molecule. In the first stage of this work, we
rigorously compare and test four recent quantum mechanical/molecular
mechanical (QM/MM) explicit solvation models, employing a QM description
of water molecules in spherical regions around both the oxygen and
the nitrogen atom of the solute. The accuracy of the models is benchmarked
against a reference QM simulation, focusing on properties of the solvated
Me2N–(CH2)3–CH=O
molecule in its ring-closed form. In the second stage, we select one
of the models (continuous adaptive QM/MM) and use it to obtain a reliable
free energy profile for the N|···C bond formation reaction.
We find that the dual-sphere approach allows the model to accurately
account for solvent reorganization along the entire reaction path.
In contrast, a simple microsolvation model cannot adapt to the changing
conditions and provides an incorrect description of the reaction process.
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Affiliation(s)
- Jelle M Boereboom
- Inorganic Chemistry and Catalysis Group, Debye Institute for Nanomaterials Science , Utrecht University , Universiteitsweg 99 , 3584 CG Utrecht , The Netherlands
| | - Paul Fleurat-Lessard
- Institut de Chimie Moléculaire de l'Université de Bourgogne (ICMUB, UMR-CNRS 6302) , Université de Bourgogne Franche-Comté , 9 Avenue Alain Savary , 21078 Dijon Cedex , France
| | - Rosa E Bulo
- Inorganic Chemistry and Catalysis Group, Debye Institute for Nanomaterials Science , Utrecht University , Universiteitsweg 99 , 3584 CG Utrecht , The Netherlands
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15
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Kiani FA, Fischer S. Comparing the catalytic strategy of ATP hydrolysis in biomolecular motors. Phys Chem Chem Phys 2018; 18:20219-33. [PMID: 27296627 DOI: 10.1039/c6cp01364c] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
ATP-driven biomolecular motors utilize the chemical energy obtained from the ATP hydrolysis to perform vital tasks in living cells. Understanding the mechanism of enzyme-catalyzed ATP hydrolysis reaction has substantially progressed lately thanks to combined quantum/classical molecular mechanics (QM/MM) simulations. Here, we present a comparative summary of the most recent QM/MM results for myosin, kinesin and F1-ATPase motors. These completely different motors achieve the acceleration of ATP hydrolysis through a very similar catalytic mechanism. ATP hydrolysis has high activation energy because it involves the breaking of two strong bonds, namely the Pγ-Oβγ bond of ATP and the H-O bond of lytic water. The key to the four-fold decrease in the activation barrier by the three enzymes is that the breaking of the Pγ-Oβγ bond precedes the deprotonation of the lytic water molecule, generating a metaphosphate hydrate complex. The resulting singly charged trigonal planar PγO3(-) metaphosphate is a better electrophilic target for attack by an OaH(-) hydroxyl group. The formation of this OaH(-) is promoted by a strong polarization of the lytic water: in all three proteins, this water is forming a hydrogen-bond with a backbone carbonyl group and interacts with the carboxylate group of glutamate (either directly or via an intercalated water molecule). This favors the shedding of one proton by the attacking water. The abstracted proton is transferred to the γ-phosphate via various proton wires, resulting in a H2PγO4(-)/ADP(3-) product state. This catalytic strategy is so effective that most other nucleotide hydrolyzing enzymes adopt a similar approach, as suggested by their very similar triphosphate binding sites.
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Affiliation(s)
- Farooq Ahmad Kiani
- Interdisciplinary Center for Scientific Computing (IWR), University of Heidelberg, Im Neuenheimer Feld 205, D-69120 Heidelberg, Germany. and Research Center for Modeling and Simulation (RCMS), National University of Sciences and Technology (NUST), Sector H-12, 44000, Islamabad, Pakistan.
| | - Stefan Fischer
- Interdisciplinary Center for Scientific Computing (IWR), University of Heidelberg, Im Neuenheimer Feld 205, D-69120 Heidelberg, Germany.
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16
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Hassan HA, Rani S, Fatima T, Kiani FA, Fischer S. Effect of protonation on the mechanism of phosphate monoester hydrolysis and comparison with the hydrolysis of nucleoside triphosphate in biomolecular motors. Biophys Chem 2017; 230:27-35. [PMID: 28941815 DOI: 10.1016/j.bpc.2017.08.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 07/31/2017] [Accepted: 08/13/2017] [Indexed: 11/25/2022]
Abstract
Hydrolysis of phosphate groups is a crucial reaction in living cells. It involves the breaking of two strong bonds, i.e. the OaH bond of the attacking water molecule, and the POl bond of the substrate (Oa and Ol stand for attacking and leaving oxygen atoms). Mechanism of the hydrolysis reaction can proceed either by a concurrent or a sequential mechanism. In the concurrent mechanism, the breaking of OaH and POl bonds occurs simultaneously, whereas in the sequential mechanism, the OaH and POl bonds break at different stages of the reaction. To understand how protonation affects the mechanism of hydrolysis of phosphate monoester, we have studied the mechanism of hydrolysis of protonated and deprotonated phosphate monoester at M06-2X/6-311+G**//M06-2X/6-31+G*+ZPE level of theory (where ZPE stands for zero point energy). Our calculations show that in both protonated and deprotonated cases, the breaking of the water OaH bond occurs before the breaking of the POl bond. Because the two events are not separated by a stable intermediate, the mechanism can be categorized as semi-concurrent. The overall energy barrier is 41kcalmol-1 in the unprotonated case. Most (5/6th) of this is due to the initial breaking of the water OaH bond. This component is lowered from 34 to 25kcalmol-1 by adding one proton to the phosphate. The rest of the overall energy barrier comes from the subsequent breaking of the POl bond and is not sensitive to protonation. This is consistent with previous findings about the effect of triphosphate protonation on the hydrolysis, where the equivalent protonation (on the γ-phosphate) was seen to lower the barrier of breaking the water OaH bond and to have little effect on the POl bond breaking. Hydrolysis pathways of phosphate monoester with initial breaking of the POl bond could not be found here. This is because the leaving group in phosphate monoester cannot be protonated, unlike in triphosphate hydrolysis, where protonation of the β- and γ-phosphates had been shown to promote a mechanism where the POl bond breaks before the OaH bond does. We also point out that the charge shift due to POl bond breaking during sequential ATP hydrolysis in bio-molecular motors onsets the week unbinding of hydrolysis product that finally leads to the product release during power stroke.
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Affiliation(s)
- Hammad Ali Hassan
- Research Center for Modeling and Simulation (RCMS), National University of Sciences and Technology (NUST), 44000 Islamabad, Pakistan
| | - Sadaf Rani
- Research Center for Modeling and Simulation (RCMS), National University of Sciences and Technology (NUST), 44000 Islamabad, Pakistan
| | - Tabeer Fatima
- Research Center for Modeling and Simulation (RCMS), National University of Sciences and Technology (NUST), 44000 Islamabad, Pakistan; Department of Biotechnology, University of Gujrat Sialkot Sub Campus, 51310 Sialkot, Pakistan
| | - Farooq Ahmad Kiani
- Research Center for Modeling and Simulation (RCMS), National University of Sciences and Technology (NUST), 44000 Islamabad, Pakistan; Department of Physiology and Biophysics, Boston University School of Medicine, 700 Albany street, 02118 Boston, MA, United States.
| | - Stefan Fischer
- Interdisciplinary Center for Scientific Computing (IWR), University of Heidelberg, Im Neuenheimer Feld 205, D-69120 Heidelberg, Germany
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17
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Barrozo A, Blaha-Nelson D, Williams NH, Kamerlin SCL. The effect of magnesium ions on triphosphate hydrolysis. PURE APPL CHEM 2017. [DOI: 10.1515/pac-2016-1125] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
AbstractThe role of metal ions in catalyzing phosphate ester hydrolysis has been the subject of much debate, both in terms of whether they change the transition state structure or mechanistic pathway. Understanding the impact of metal ions on these biologically critical reactions is central to improving our understanding of the role of metal ions in the numerous enzymes that facilitate them. In the present study, we have performed density functional theory studies of the mechanisms of methyl triphosphate and acetyl phosphate hydrolysis in aqueous solution to explore the competition between solvent- and substrate-assisted pathways, and examined the impact of Mg2+ on the energetics and transition state geometries. In both cases, we observe a clear preference for a more dissociative solvent-assisted transition state, which is not significantly changed by coordination of Mg2+. The effect of Mg2+ on the transition state geometries for the two pathways is minimal. While our calculations cannot rule out a substrate-assisted pathway as a possible solution for biological phosphate hydrolysis, they demonstrate that a significantly higher energy barrier needs to be overcome in the enzymatic reaction for this to be an energetically viable reaction pathway.
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Affiliation(s)
- Alexandre Barrozo
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089-1062, USA
| | - David Blaha-Nelson
- Department of Cell and Molecular Biology, Uppsala University, BMC Box 596, S-751 24 Uppsala, Sweden
| | | | - Shina C. L. Kamerlin
- Department of Cell and Molecular Biology, Uppsala University, BMC Box 596, S-751 24 Uppsala, Sweden
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18
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Wang J, Wang Z, Ling B, Cao N, Wang W. Identification of a potential proton donor to the linking oxygen atom in a three-metal ion assisted catalysis pathway catalyzed by Fructose-1, 6-bisphosphatase. J Mol Graph Model 2017; 73:191-199. [PMID: 28301812 DOI: 10.1016/j.jmgm.2017.01.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 12/16/2016] [Accepted: 01/04/2017] [Indexed: 12/01/2022]
Abstract
In this paper, the dephosphorylation mechanism of FBP to F6P catalyzed by the Fructose-1, 6-bisphosphatase (St-Fbp) from Sulfolobus tokodaii was studied using quantum mechanical/molecular mechanical (QM/MM) approach. Based on the experimental results, total five possible catalytic mechanisms (path1-path4') were designed. The most possible dephosphorylation reaction follows a two-step mechanism (path2): a dephosphorylation process (with D12 being an base of W6 and residue K133 being the proton donor of the linking FBP:O4) and a proton exchange process (between K133 and the water W1). Furthermore, the three-step of path4 is also possible: a dephosphorylation process (with D54 being the base of W6 and residue K133 being the proton donor of the linking FBP:O4) and two proton exchange processes (first between residues D54 and D12 then between K133 and the water W1). The relative low energy of this pathway suggests that D54 might also be a base except D12. Our calculations indicate that K133 is the preferred proton donor during the breaking of the phosphate bond O4-P1, with the W1 being an alternative proton donor to access to a more stable product. Findings here give a new insight into the understanding of catalytic mechanism of FBPase.
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Affiliation(s)
- Jinhu Wang
- College of Chemistry, Chemical Engineering and Material Science, Zaozhuang University, Zaozhuang, Shandong 277160, China.
| | - Zhiguo Wang
- Institute of Aging Research, School of Medicine, Hangzhou Normal University, Hangzhou 311121, China.
| | - Baoping Ling
- College of Chemistry Chemical Engineering, Qufu Normal University, Qufu, Shandong 273165, China
| | - Nan Cao
- College of Chemistry, Chemical Engineering and Material Science, Zaozhuang University, Zaozhuang, Shandong 277160, China
| | - Wen Wang
- College of Chemistry, Chemical Engineering and Material Science, Zaozhuang University, Zaozhuang, Shandong 277160, China
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19
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Tripathi R, Glaves R, Marx D. The GTPase hGBP1 converts GTP to GMP in two steps via proton shuttle mechanisms. Chem Sci 2017; 8:371-380. [PMID: 28451182 PMCID: PMC5365056 DOI: 10.1039/c6sc02045c] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Accepted: 08/21/2016] [Indexed: 11/21/2022] Open
Abstract
GTPases play a crucial role in the regulation of many biological processes by catalyzing the hydrolysis of GTP into GDP. The focus of this work is on the dynamin-related large GTPase human guanine nucleotide binding protein-1 (hGBP1) which is able to hydrolyze GTP even to GMP. Here, we studied the largely unknown mechanisms of both GTP and GDP hydrolysis steps utilizing accelerated ab initio QM/MM metadynamics simulations to compute multi-dimensional free energy landscapes. We find an indirect substrate-assisted catalysis (SAC) mechanism for GTP hydrolysis involving transfer of a proton from the water nucleophile to a nonbridging phosphoryl oxygen via a proton relay pathway where the rate-determining first step is concerted-dissociative nature. A "composite base" consisting of Ser73, Glu99, a bridging water molecule, and GTP was found to activate the nucleophilic water, thus disclosing the complex nature of the general base in hGBP1. A nearly two-fold reduction in the free energy barrier was obtained for GTP hydrolysis in the enzyme in comparison to bulk solvent. The subsequent GDP hydrolysis in hGBP1 was also found to follow a water-mediated proton shuttle mechanism. It is expected that the proton shuttle mechanisms unravelled for hGBP1 apply to many classes of GTPases/ATPases that possess an optimally-arranged hydrogen bonding network, which connects the catalytic water to a proton acceptor.
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Affiliation(s)
- Ravi Tripathi
- Lehrstuhl für Theoretische Chemie , Ruhr-Universität Bochum , 44780 Bochum , Germany .
| | - Rachel Glaves
- Lehrstuhl für Theoretische Chemie , Ruhr-Universität Bochum , 44780 Bochum , Germany .
| | - Dominik Marx
- Lehrstuhl für Theoretische Chemie , Ruhr-Universität Bochum , 44780 Bochum , Germany .
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20
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Vithani N, Batra S, Prakash B, Nair NN. Elucidating the GTP Hydrolysis Mechanism in FeoB: A Hydrophobic Amino-Acid Substituted GTPase. ACS Catal 2016. [DOI: 10.1021/acscatal.6b03365] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Neha Vithani
- Department
of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur 208016, India
| | - Sahil Batra
- Department
of Biological Sciences and Bioengineering, Indian Institute of Technology, Kanpur 208016, India
| | - Balaji Prakash
- Department
of Molecular Nutrition, CSIR-Central Food Technological Research Institute, Mysore, 570020, India
| | - Nisanth N. Nair
- Department
of Chemistry, Indian Institute of Technology, Kanpur 208016, India
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21
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Hsu WL, Furuta T, Sakurai M. ATP Hydrolysis Mechanism in a Maltose Transporter Explored by QM/MM Metadynamics Simulation. J Phys Chem B 2016; 120:11102-11112. [PMID: 27712074 DOI: 10.1021/acs.jpcb.6b07332] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Translocation of substrates across the cell membrane by adenosine 5'-triphosphate (ATP)-binding cassette (ABC) transporters depends on the energy provided by ATP hydrolysis within the nucleotide-binding domains (NBDs). However, the detailed mechanism remains unclear. In this study, we focused on maltose transporter NBDs (MalK2) and performed a quantum mechanical/molecular mechanical (QM/MM) well-tempered metadynamics simulation to address this issue. We explored the free-energy profile along an assigned collective variable. As a result, it was determined that the activation free energy is approximately 10.5 kcal/mol, and the reaction released approximately 3.8 kcal/mol of free energy, indicating that the reaction of interest is a one-step exothermic reaction. The dissociation of the ATP γ-phosphate seems to be the rate-limiting step, which supports the so-called dissociative model. Moreover, Glu159, located in the Walker B motif, acts as a base to abstract the proton from the lytic water, but is not the catalytic base, which corresponds to an atypical general base catalysis model. We also observed two interesting proton transfers: transfer from the His192 ε-position nitrogen to the dissociated inorganic phosphate, Pi, and transfer from the Lys42 side chain to adenosine 5'-diphosphate β-phosphate. These proton transfers would stabilize the posthydrolysis state. Our study provides significant insight into the ATP hydrolysis mechanism in MalK2 from a dynamical viewpoint, and this insight would be applicable to other ABC transporters.
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Affiliation(s)
- Wei-Lin Hsu
- Center for Biological Resources and Informatics, Tokyo Institute of Technology , 4259-B-62, Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan
| | - Tadaomi Furuta
- Center for Biological Resources and Informatics, Tokyo Institute of Technology , 4259-B-62, Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan
| | - Minoru Sakurai
- Center for Biological Resources and Informatics, Tokyo Institute of Technology , 4259-B-62, Nagatsuta-cho, Midori-ku, Yokohama 226-8501, Japan
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22
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Kiani FA, Fischer S. Effects of protonation on the hydrolysis of triphosphate in vacuum and the implications for catalysis by nucleotide hydrolyzing enzymes. BMC BIOCHEMISTRY 2016; 17:12. [PMID: 27974044 PMCID: PMC5157097 DOI: 10.1186/s12858-016-0068-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Accepted: 06/14/2016] [Indexed: 11/15/2022]
Abstract
BACKGROUND Nucleoside triphosphate (NTP) hydrolysis is a key reaction in biology. It involves breaking two very stable bonds (one P-O bond and one O-H bond of water), in either a concurrent or a sequential way. Here, we systematically examine how protonation of the triphosphate affects the mechanism of hydrolysis. RESULTS The hydrolysis reaction of methyl triphosphate in vacuum is computed with protons in various numbers and position on the three phosphate groups. Protonation is seen to have a strong catalytic effect, with the reaction mechanism depending highly on the protonation pattern. CONCLUSION This dependence is apparently complicated, but is shown to obey a well-defined set of rules: Protonation of the α- and β-phosphate groups favors a sequential hydrolysis mechanism, whereas γ-protonation favors a concurrent mechanism, the two effects competing with each other in cases of simultaneous protonation. The rate-limiting step is always the breakup of the water molecule while it attacks the γ-phosphorus, and its barrier is lowered by γ-protonation. This step has significantly lower barriers in the sequential reactions, because the dissociated γ-metaphosphate intermediate (PγO3-) is a much better target for water attack than the un-dissociated γ-phosphate (-PγO42-). The simple chemical logic behind these rules helps to better understand the catalytic strategy used by NTPase enzymes, as illustrated here for the catalytic pocket of myosin. A set of rules was determined that describes how protonating the phosphate groups affects the hydrolysis mechanism of methyl triphosphate: Protonation of the α- and/or β- phosphate groups promotes a sequential mechanism in which P-O bond breaking precedes the breakup of the attacking water, whereas protonation of the γ-phosphate promotes a concurrent mechanism and lowers the rate-limiting barrier of water breakup. The role played by individual protein residues in the catalytic pocket of triphosphate hydrolysing enzymes can be assigned accordingly.
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Affiliation(s)
- Farooq Ahmad Kiani
- Research Center for Modeling and Simulation (RCMS), National University of Sciences and Technology (NUST), Sector H-12, 44000 Islamabad, Pakistan
| | - Stefan Fischer
- Computational Biochemistry, Interdisciplinary Center for Scientific Computing (IWR), Heidelberg University, Im Neuenheimer Feld 205, D-69120 Heidelberg, Germany
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23
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Wang C, Huang W, Liao JL. QM/MM investigation of ATP hydrolysis in aqueous solution. J Phys Chem B 2015; 119:3720-6. [PMID: 25658024 DOI: 10.1021/jp512960e] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Adenosine-5'-triphosphate (ATP) hydrolysis represents a most important reaction in biology. Despite extensive research efforts, the mechanism for ATP hydrolysis in aqueous solution still remains under debate. Previous theoretical studies often predefined reaction coordinates to characterize the mechanism for ATP hydrolysis in water with Mg(2+) by evaluating free energy profiles through these preassumed reaction paths. In the present work, a nudged elastic band method is applied to identify the minimum energy path calculated with a hybrid quantum mechanics and molecular mechanics approach. Along the reaction path, the free energy profile was obtained to have a single transition state and the activation energy of 32.5 kcal/mol. This transition state bears a four-centered structure that describes a concerted nature of the reaction. In the More-O'Ferrall-Jencks diagram, the results show that the reaction proceeds through a concerted path before the system reaches the transition state and along an associative path after the transition state. In addition, the calculated reaction free energy is -7.0 kcal/mol, in good agreement with experiment, capturing the exothermic feature of MgATP(2-) hydrolysis in aqueous solution, whereas the reaction was often shown to be endothermic in the previous theoretical studies. As Mg(2+) is required for ATP hydrolysis in cells, its role in the reaction is also elucidated.
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Affiliation(s)
- Cui Wang
- Department of Chemical Physics, University of Science and Technology of China , 96 Jinzhai Road, 230026 Hefei, Anhui Province, People's Republic of China
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24
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Kale S, Sode O, Weare J, Dinner AR. Finding Chemical Reaction Paths with a Multilevel Preconditioning Protocol. J Chem Theory Comput 2014; 10:5467-5475. [PMID: 25516726 PMCID: PMC4263463 DOI: 10.1021/ct500852y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Indexed: 11/28/2022]
Abstract
Finding transition paths for chemical reactions can be computationally costly owing to the level of quantum-chemical theory needed for accuracy. Here, we show that a multilevel preconditioning scheme that was recently introduced (Tempkin et al. J. Chem. Phys.2014, 140, 184114) can be used to accelerate quantum-chemical string calculations. We demonstrate the method by finding minimum-energy paths for two well-characterized reactions: tautomerization of malonaldehyde and Claissen rearrangement of chorismate to prephanate. For these reactions, we show that preconditioning density functional theory (DFT) with a semiempirical method reduces the computational cost for reaching a converged path that is an optimum under DFT by several fold. The approach also shows promise for free energy calculations when thermal noise can be controlled.
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Affiliation(s)
- Seyit Kale
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, Computation Institute, Department of Statistics, University of Chicago , Chicago, Illinois 60637, United States ; Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, Computation Institute, Department of Statistics, University of Chicago , Chicago, Illinois 60637, United States
| | - Olaseni Sode
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, Computation Institute, Department of Statistics, University of Chicago , Chicago, Illinois 60637, United States ; Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, Computation Institute, Department of Statistics, University of Chicago , Chicago, Illinois 60637, United States ; Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, Computation Institute, Department of Statistics, University of Chicago , Chicago, Illinois 60637, United States ; Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, Computation Institute, Department of Statistics, University of Chicago , Chicago, Illinois 60637, United States ; Computing, Environment, and Life Sciences, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Jonathan Weare
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, Computation Institute, Department of Statistics, University of Chicago , Chicago, Illinois 60637, United States ; Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, Computation Institute, Department of Statistics, University of Chicago , Chicago, Illinois 60637, United States ; Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, Computation Institute, Department of Statistics, University of Chicago , Chicago, Illinois 60637, United States
| | - Aaron R Dinner
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, Computation Institute, Department of Statistics, University of Chicago , Chicago, Illinois 60637, United States ; Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, Computation Institute, Department of Statistics, University of Chicago , Chicago, Illinois 60637, United States ; Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, Computation Institute, Department of Statistics, University of Chicago , Chicago, Illinois 60637, United States ; Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, Computation Institute, Department of Statistics, University of Chicago , Chicago, Illinois 60637, United States
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25
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Duarte F, Åqvist J, Williams NH, Kamerlin SCL. Resolving apparent conflicts between theoretical and experimental models of phosphate monoester hydrolysis. J Am Chem Soc 2014; 137:1081-93. [PMID: 25423607 PMCID: PMC4311964 DOI: 10.1021/ja5082712] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
![]()
Understanding
phosphoryl and sulfuryl transfer is central to many
biochemical processes. However, despite decades of experimental and
computational studies, a consensus concerning the precise mechanistic
details of these reactions has yet to be reached. In this work we
perform a detailed comparative theoretical study of the hydrolysis
of p-nitrophenyl phosphate, methyl phosphate and p-nitrophenyl sulfate, all of which have served as key model
systems for understanding phosphoryl and sulfuryl transfer reactions,
respectively. We demonstrate the existence of energetically similar
but mechanistically distinct possibilities for phosphate monoester
hydrolysis. The calculated kinetic isotope effects for p-nitrophenyl phosphate provide a means to discriminate between substrate-
and solvent-assisted pathways of phosphate monoester hydrolysis, and
show that the solvent-assisted pathway dominates in solution. This
preferred mechanism for p-nitrophenyl phosphate hydrolysis
is difficult to find computationally due to the limitations of compressing
multiple bonding changes onto a 2-dimensional energy surface. This
problem is compounded by the need to include implicit solvation to
at least microsolvate the system and stabilize the highly charged
species. In contrast, methyl phosphate hydrolysis shows a preference
for a substrate-assisted mechanism. For p-nitrophenyl
sulfate hydrolysis there is only one viable reaction pathway, which
is similar to the solvent-assisted pathway for phosphate hydrolysis,
and the substrate-assisted pathway is not accessible. Overall, our
results provide a unifying mechanistic framework that is consistent
with the experimentally measured kinetic isotope effects and reconciles
the discrepancies between theoretical and experimental models for
these biochemically ubiquitous classes of reaction.
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Affiliation(s)
- Fernanda Duarte
- Department of Cell and Molecular Biology (ICM), Uppsala University , SE-751 24 Uppsala, Sweden
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26
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McCullagh M, Saunders MG, Voth GA. Unraveling the mystery of ATP hydrolysis in actin filaments. J Am Chem Soc 2014; 136:13053-8. [PMID: 25181471 PMCID: PMC4183606 DOI: 10.1021/ja507169f] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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Actin
performs its myriad cellular functions by the growth and
disassembly of its filamentous form. The hydrolysis of ATP in the
actin filament has been shown to modulate properties of the filament,
thus making it a pivotal regulator of the actin life cycle. Actin
has evolved to selectively hydrolyze ATP in the filamentous form,
F-actin, with an experimentally observed rate increase over the monomeric
form, G-actin, of 4.3 × 104. The cause of this dramatic
increase in rate is investigated in this paper using extensive QM/MM
simulations of both G- and F-actin. To compute the free energy of
hydrolysis in both systems, metadynamics is employed along two collective
variables chosen to describe the reaction coordinates of hydrolysis.
F-actin is modeled as a monomer with restraints applied to coarse-grained
variables enforced to keep it in a filament-like conformation. The
simulations reveal a barrier height reduction for ATP hydrolysis in
F-actin as compared to G-actin of 8 ± 1 kcal/mol, in good agreement
with the experimentally measured barrier height reduction of 7 ±
1 kcal/mol. The barrier height reduction is influenced by an enhanced
rotational diffusion of water in F-actin as compared to G-actin and
shorter water wires between Asp154 and the nucleophilic water in F-actin,
leading to more rapid proton transport.
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Affiliation(s)
- Martin McCullagh
- Department of Chemistry, James Franck Institute, Institute for Biophysical Dynamics, and Computation Institute, The University of Chicago , Chicago, Illinois 60637, United States
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27
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Zheng S, Pfaendtner J. Enhanced sampling of chemical and biochemical reactions with metadynamics. MOLECULAR SIMULATION 2014. [DOI: 10.1080/08927022.2014.923574] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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28
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Elsässer B, Fels G, Weare JH. QM/MM simulation (B3LYP) of the RNase A cleavage-transesterification reaction supports a triester A(N) + D(N) associative mechanism with an O2' H internal proton transfer. J Am Chem Soc 2014; 136:927-36. [PMID: 24372083 DOI: 10.1021/ja406122c] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The mechanism of the backbone cleavage-transesterification step of the RNase A enzyme remains controversial even after 60 years of study. We report quantum mechanics/molecule mechanics (QM/MM) free energy calculations for two optimized reaction paths based on an analysis of all structural data and identified by a search for reaction coordinates using a reliable quantum chemistry method (B3LYP), equilibrated structural optimizations, and free energy estimations. Both paths are initiated by nucleophilic attack of the ribose O2' oxygen on the neighboring diester phosphate bond, and both reach the same product state (PS) (a O3'-O2' cyclic phosphate and a O5' hydroxyl terminated fragment). Path 1, resembles the widely accepted dianionic transition-state (TS) general acid (His119)/base (His12) classical mechanism. However, this path has a barrier (25 kcal/mol) higher than that of the rate-limiting hydrolysis step and a very loose TS. In Path 2, the proton initially coordinating the O2' migrates to the nonbridging O1P in the initial reaction path rather than directly to the general base resulting in a triester (substrate as base) AN + DN mechanism with a monoanionic weakly stable intermediate. The structures in the transition region are associative with low barriers (TS1 10, TS2 7.5 kcal/mol). The Path 2 mechanism is consistent with the many results from enzyme and buffer catalyzed and uncatalyzed analog reactions and leads to a PS consistent with the reactive state for the following hydrolysis step. The differences between the consistently estimated barriers in Path 1 and 2 lead to a 10(11) difference in rate strongly supporting the less accepted triester mechanism.
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Affiliation(s)
- Brigitta Elsässer
- Department of Chemistry, University of Paderborn , Warburgerstr. 100, D-33098 Paderborn, Germany
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29
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Quantitative exploration of the molecular origin of the activation of GTPase. Proc Natl Acad Sci U S A 2013; 110:20509-14. [PMID: 24282301 DOI: 10.1073/pnas.1319854110] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
GTPases play a major role in cellular processes, and gaining quantitative understanding of their activation demands reliable free energy surfaces of the relevant mechanistic paths in solution, as well as the interpolation of this information to GTPases. Recently, we generated ab initio quantum mechanical/molecular mechanical free energy surfaces for the hydrolysis of phosphate monoesters in solution, establishing quantitatively that the barrier for the reactions with a proton transfer (PT) step from a single attacking water (1 W) is higher than the one where the PT is assisted by a second water (2 W). The implication of this finding on the activation of GTPases is quantified here, by using the ab initio solution surfaces to calibrate empirical valence bond surfaces and then exploring the origin of the activation effect. It is found that, although the 2 W PT path is a new element, this step is not rate determining, and the catalytic effect is actually due to the electrostatic stabilization of the pre-PT transition state and the subsequent plateau. Thus, the electrostatic catalytic effect found in our previous studies of the Ras GTPase activating protein (RasGAP) and the elongation factor-Tu (EF-Tu) with a 1 W mechanism is still valid for the 2 W path. Furthermore, as found before, the corresponding activation appears to involve a major allosteric effect. Overall, we believe that our finding is general to both GTPases and ATPases. In addition to the biologically relevant finding, we also provide a critical discussion of the requirements from reliable surfaces for enzymatic reactions.
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30
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McGrath MJ, Kuo IFW, Hayashi S, Takada S. Adenosine triphosphate hydrolysis mechanism in kinesin studied by combined quantum-mechanical/molecular-mechanical metadynamics simulations. J Am Chem Soc 2013; 135:8908-19. [PMID: 23751065 DOI: 10.1021/ja401540g] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Kinesin is a molecular motor that hydrolyzes adenosine triphosphate (ATP) and moves along microtubules against load. While motility and atomic structures have been well-characterized for various members of the kinesin family, not much is known about ATP hydrolysis inside the active site. Here, we study ATP hydrolysis mechanisms in the kinesin-5 protein Eg5 by using combined quantum mechanics/molecular mechanics metadynamics simulations. Approximately 200 atoms at the catalytic site are treated by a dispersion-corrected density functional and, in total, 13 metadynamics simulations are performed with their cumulative time reaching ~0.7 ns. Using the converged runs, we compute free energy surfaces and obtain a few hydrolysis pathways. The pathway with the lowest free energy barrier involves a two-water chain and is initiated by the Pγ-Oβ dissociation concerted with approach of the lytic water to PγO3-. This immediately induces a proton transfer from the lytic water to another water, which then gives a proton to the conserved Glu270. Later, the proton is transferred back from Glu270 to HPO(4)2- via another hydrogen-bonded chain. We find that the reaction is favorable when the salt bridge between Glu270 in switch II and Arg234 in switch I is transiently broken, which facilitates the ability of Glu270 to accept a proton. When ATP is placed in the ADP-bound conformation of Eg5, the ATP-Mg moiety is surrounded by many water molecules and Thr107 blocks the water chain, which together make the hydrolysis reaction less favorable. The observed two-water chain mechanisms are rather similar to those suggested in two other motors, myosin and F1-ATPase, raising the possibility of a common mechanism.
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Affiliation(s)
- Matthew J McGrath
- Department of Biophysics, Graduate School of Science, Kyoto University, Sakyo, Kyoto 606-8502, Japan.
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31
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Plotnikov NV, Prasad BR, Chakrabarty S, Chu ZT, Warshel A. Quantifying the mechanism of phosphate monoester hydrolysis in aqueous solution by evaluating the relevant ab initio QM/MM free-energy surfaces. J Phys Chem B 2013; 117:12807-19. [PMID: 23601038 DOI: 10.1021/jp4020146] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Understanding the nature of the free-energy surfaces for phosphate hydrolysis is a prerequisite for understanding the corresponding key chemical reactions in biology. Here, the challenge has been to move to careful ab initio QM/MM (QM(ai)/MM) free-energy calculations, where obtaining converging results is very demanding and computationally expensive. This work describes such calculations, focusing on the free-energy surface for the hydrolysis of phosphate monoesters, paying special attention to the comparison between the one water (1W) and two water (2W) paths for the proton-transfer (PT) step. This issue has been explored before by energy minimization with implicit solvent models and by nonsystematic QM/MM energy minimization, as well as by nonsystematic free-energy mapping. However, no study has provided the needed reliable 2D (3D) surfaces that are necessary for reaching concrete conclusions. Here we report a systematic evaluation of the 2D (3D) free-energy maps for several relevant systems, comparing the results of QM(ai)/MM and QM(ai)/implicit solvent surfaces, and provide an advanced description of the relevant energetics. It is found that the 1W path for the hydrolysis of the methyl diphosphate (MDP) trianion is 6-9 kcal/mol higher than that the 2W path. This difference becomes slightly larger in the presence of the Mg(2+) ion because this ion reduces the pKa of the conjugated acid form of the phosphate oxygen that accepts the proton. Interestingly, the BLYP approach (which has been used extensively in some studies) gives a much smaller difference between the 1W and 2W activation barriers. At any rate, it is worth pointing out that the 2W transition state for the PT is not much higher that the common plateau that serves as the starting point of both the 1W and 2W PT paths. Thus, the calculated catalytic effects of proteins based on the 2W PT mechanistic model are not expected to be different from the catalytic effects predicted using the 1W PT mechanistic model, which was calibrated on the observed barrier in solution and in which the TS charge distribution was similar to the that of the plateau (as was done in all of our previous EVB studies).
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Affiliation(s)
- Nikolay V Plotnikov
- Department of Chemistry, University of Southern California , SGM 418, 3620 McClintock Avenue, Los Angeles, California 90089, United States
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32
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Abstract
Phosphoryl transfer plays key roles in signaling, energy transduction, protein synthesis, and maintaining the integrity of the genetic material. On the surface, it would appear to be a simple nucleophile displacement reaction. However, this simplicity is deceptive, as, even in aqueous solution, the low-lying d-orbitals on the phosphorus atom allow for eight distinct mechanistic possibilities, before even introducing the complexities of the enzyme catalyzed reactions. To further complicate matters, while powerful, traditional experimental techniques such as the use of linear free-energy relationships (LFER) or measuring isotope effects cannot make unique distinctions between different potential mechanisms. A quarter of a century has passed since Westheimer wrote his seminal review, 'Why Nature Chose Phosphate' (Science 235 (1987), 1173), and a lot has changed in the field since then. The present review revisits this biologically crucial issue, exploring both relevant enzymatic systems as well as the corresponding chemistry in aqueous solution, and demonstrating that the only way key questions in this field are likely to be resolved is through careful theoretical studies (which of course should be able to reproduce all relevant experimental data). Finally, we demonstrate that the reason that nature really chose phosphate is due to interplay between two counteracting effects: on the one hand, phosphates are negatively charged and the resulting charge-charge repulsion with the attacking nucleophile contributes to the very high barrier for hydrolysis, making phosphate esters among the most inert compounds known. However, biology is not only about reducing the barrier to unfavorable chemical reactions. That is, the same charge-charge repulsion that makes phosphate ester hydrolysis so unfavorable also makes it possible to regulate, by exploiting the electrostatics. This means that phosphate ester hydrolysis can not only be turned on, but also be turned off, by fine tuning the electrostatic environment and the present review demonstrates numerous examples where this is the case. Without this capacity for regulation, it would be impossible to have for instance a signaling or metabolic cascade, where the action of each participant is determined by the fine-tuned activity of the previous piece in the production line. This makes phosphate esters the ideal compounds to facilitate life as we know it.
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33
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Prasad BR, Plotnikov NV, Warshel A. Addressing open questions about phosphate hydrolysis pathways by careful free energy mapping. J Phys Chem B 2012. [PMID: 23198768 DOI: 10.1021/jp309778n] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The nature and mechanism of phosphate hydrolysis reactions are of great interest in view of the crucial role of these reactions in key biological processes. Although it is becoming clearer that the ultimate way of resolving mechanistic controversies must involve reliable theoretical studies, it is not widely realized that such studies cannot be performed at present by using most existing automated ways and that only careful systematic studies can lead to meaningful conclusions. The present work clarifies the above point by considering the hydrolysis of phosphate monoesters. The clarification starts by defining the actual issues that should be addressed in careful studies and by highlighting the problems with studies that ignore the need for unique mechanistic definitions (e.g., works that confuse associative and dissociative pathways). We then focus on the analysis of the proton transfer (PT) pathways in phosphate hydrolysis and on recent suggestions that PT involves more than one water molecule. Here we point out that most of the studies that found a proton transfer through several water molecules have not involved a sufficient systematic search of the relevant reaction coordinates. This includes both energy minimization approaches as well as a recent metadynamics (MTD) simulation study. To illustrate the crucial need of exploring the potential surfaces reliably, rather than relying on automated approaches, we present here a very careful study of the free energy landscape along a 3D reaction coordinate (RC) exploring both the standard 2D RC, comprised of the attacking and leaving group reaction coordinates, as well as of the proton transfer (PT) coordinate. Our study points out that QM/MM minimization or MTD studies that concluded that the hydrolysis of phosphate monoesters involves a PT through several water molecules, have not explored carefully the single water (1W) path (that involves a direct PT form the attacking water molecule to the phosphate oxygen). Furthermore, we identified the most likely reason for the difficulty in finding the 1W path by QM/MM minimization methods, as well as by the current MTD simulations. We also discuss the problems with current studies that challenge the phosphate as a base mechanism and emphasize that all recent studies found associative/concerted paths (although many have not realized the meaning of their results). Finally, although we clearly do not have the last word about the 1W versus 2W paths we believe that we illustrated that the crucial mechanistic problems with alternative pathways should not be resolved by just running black box search approaches.
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Affiliation(s)
- B Ram Prasad
- Department of Chemistry, University of Southern California, SGM 418, 3620 McClintock Avenue, Los Angeles, California 90089, United States
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