1
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Klein A, Rovó P, Sakhrani VV, Wang Y, Holmes JB, Liu V, Skowronek P, Kukuk L, Vasa SK, Güntert P, Mueller LJ, Linser R. Atomic-resolution chemical characterization of (2x)72-kDa tryptophan synthase via four- and five-dimensional 1H-detected solid-state NMR. Proc Natl Acad Sci U S A 2022; 119:e2114690119. [PMID: 35058365 PMCID: PMC8795498 DOI: 10.1073/pnas.2114690119] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Accepted: 12/13/2021] [Indexed: 02/07/2023] Open
Abstract
NMR chemical shifts provide detailed information on the chemical properties of molecules, thereby complementing structural data from techniques like X-ray crystallography and electron microscopy. Detailed analysis of protein NMR data, however, often hinges on comprehensive, site-specific assignment of backbone resonances, which becomes a bottleneck for molecular weights beyond 40 to 45 kDa. Here, we show that assignments for the (2x)72-kDa protein tryptophan synthase (665 amino acids per asymmetric unit) can be achieved via higher-dimensional, proton-detected, solid-state NMR using a single, 1-mg, uniformly labeled, microcrystalline sample. This framework grants access to atom-specific characterization of chemical properties and relaxation for the backbone and side chains, including those residues important for the catalytic turnover. Combined with first-principles calculations, the chemical shifts in the β-subunit active site suggest a connection between active-site chemistry, the electrostatic environment, and catalytically important dynamics of the portal to the β-subunit from solution.
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Affiliation(s)
- Alexander Klein
- Department of Chemistry and Pharmacy, Ludwig Maximilians University, 81377 Munich, Germany
- Department of Chemistry and Chemical Biology, TU Dortmund University, 44227 Dortmund, Germany
| | - Petra Rovó
- Department of Chemistry and Pharmacy, Ludwig Maximilians University, 81377 Munich, Germany
| | - Varun V Sakhrani
- Department of Chemistry, University of California, Riverside, CA 92521
| | - Yangyang Wang
- Department of Chemistry, University of California, Riverside, CA 92521
| | - Jacob B Holmes
- Department of Chemistry, University of California, Riverside, CA 92521
| | - Viktoriia Liu
- Department of Chemistry, University of California, Riverside, CA 92521
| | - Patricia Skowronek
- Department of Chemistry and Pharmacy, Ludwig Maximilians University, 81377 Munich, Germany
| | - Laura Kukuk
- Department of Chemistry and Chemical Biology, TU Dortmund University, 44227 Dortmund, Germany
| | - Suresh K Vasa
- Department of Chemistry and Pharmacy, Ludwig Maximilians University, 81377 Munich, Germany
- Department of Chemistry and Chemical Biology, TU Dortmund University, 44227 Dortmund, Germany
| | - Peter Güntert
- Institute of Biophysical Chemistry, Goethe University, 60438 Frankfurt am Main, Germany
- Laboratory of Physical Chemistry, Eidgenössische Technische Hochschule (ETH) Zürich, 8093 Zürich, Switzerland
- Department of Chemistry, Tokyo Metropolitan University, Tokyo 192-0397, Japan
| | - Leonard J Mueller
- Department of Chemistry, University of California, Riverside, CA 92521
| | - Rasmus Linser
- Department of Chemistry and Pharmacy, Ludwig Maximilians University, 81377 Munich, Germany;
- Department of Chemistry and Chemical Biology, TU Dortmund University, 44227 Dortmund, Germany
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2
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Holmes JB, Liu V, Caulkins BG, Hilario E, Ghosh RK, Drago VN, Young RP, Romero JA, Gill AD, Bogie PM, Paulino J, Wang X, Riviere G, Bosken YK, Struppe J, Hassan A, Guidoulianov J, Perrone B, Mentink-Vigier F, Chang CEA, Long JR, Hooley RJ, Mueser TC, Dunn MF, Mueller LJ. Imaging active site chemistry and protonation states: NMR crystallography of the tryptophan synthase α-aminoacrylate intermediate. Proc Natl Acad Sci U S A 2022; 119:e2109235119. [PMID: 34996869 PMCID: PMC8764694 DOI: 10.1073/pnas.2109235119] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/15/2021] [Indexed: 02/07/2023] Open
Abstract
NMR-assisted crystallography-the integrated application of solid-state NMR, X-ray crystallography, and first-principles computational chemistry-holds significant promise for mechanistic enzymology: by providing atomic-resolution characterization of stable intermediates in enzyme active sites, including hydrogen atom locations and tautomeric equilibria, NMR crystallography offers insight into both structure and chemical dynamics. Here, this integrated approach is used to characterize the tryptophan synthase α-aminoacrylate intermediate, a defining species for pyridoxal-5'-phosphate-dependent enzymes that catalyze β-elimination and replacement reactions. For this intermediate, NMR-assisted crystallography is able to identify the protonation states of the ionizable sites on the cofactor, substrate, and catalytic side chains as well as the location and orientation of crystallographic waters within the active site. Most notable is the water molecule immediately adjacent to the substrate β-carbon, which serves as a hydrogen bond donor to the ε-amino group of the acid-base catalytic residue βLys87. From this analysis, a detailed three-dimensional picture of structure and reactivity emerges, highlighting the fate of the L-serine hydroxyl leaving group and the reaction pathway back to the preceding transition state. Reaction of the α-aminoacrylate intermediate with benzimidazole, an isostere of the natural substrate indole, shows benzimidazole bound in the active site and poised for, but unable to initiate, the subsequent bond formation step. When modeled into the benzimidazole position, indole is positioned with C3 in contact with the α-aminoacrylate Cβ and aligned for nucleophilic attack. Here, the chemically detailed, three-dimensional structure from NMR-assisted crystallography is key to understanding why benzimidazole does not react, while indole does.
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Affiliation(s)
- Jacob B Holmes
- Department of Chemistry, University of California, Riverside, CA 92521
| | - Viktoriia Liu
- Department of Chemistry, University of California, Riverside, CA 92521
| | - Bethany G Caulkins
- Department of Chemistry, University of California, Riverside, CA 92521
- W.M. Keck Science Department, Claremont McKenna, Pitzer, and Scripps Colleges, Claremont, CA 91711
| | - Eduardo Hilario
- Department of Chemistry, University of California, Riverside, CA 92521
| | - Rittik K Ghosh
- Department of Biochemistry, University of California, Riverside, CA 92521
| | - Victoria N Drago
- Department of Chemistry and Biochemistry, University of Toledo, Toledo, OH 43606
| | - Robert P Young
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, WA 99354
| | - Jennifer A Romero
- Department of Chemistry, University of California, Riverside, CA 92521
| | - Adam D Gill
- Department of Biochemistry, University of California, Riverside, CA 92521
| | - Paul M Bogie
- Department of Chemistry, University of California, Riverside, CA 92521
| | - Joana Paulino
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310
| | - Xiaoling Wang
- National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310
| | - Gwladys Riviere
- Department of Biochemistry and Molecular Biology, McKnight Brain Institute, National High Magnetic Field Laboratory, University of Florida, Gainesville, FL 32610
| | - Yuliana K Bosken
- Department of Biochemistry, University of California, Riverside, CA 92521
| | | | - Alia Hassan
- Bruker Switzerland AG 8117 Fällanden, Switzerland
| | | | | | | | - Chia-En A Chang
- Department of Chemistry, University of California, Riverside, CA 92521
| | - Joanna R Long
- Department of Biochemistry and Molecular Biology, McKnight Brain Institute, National High Magnetic Field Laboratory, University of Florida, Gainesville, FL 32610
| | - Richard J Hooley
- Department of Chemistry, University of California, Riverside, CA 92521
- Department of Biochemistry, University of California, Riverside, CA 92521
| | - Timothy C Mueser
- Department of Chemistry and Biochemistry, University of Toledo, Toledo, OH 43606
| | - Michael F Dunn
- Department of Biochemistry, University of California, Riverside, CA 92521;
| | - Leonard J Mueller
- Department of Chemistry, University of California, Riverside, CA 92521;
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3
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O'Rourke KF, D'Amico RN, Sahu D, Boehr DD. Distinct conformational dynamics and allosteric networks in alpha tryptophan synthase during active catalysis. Protein Sci 2020; 30:543-557. [PMID: 33314435 DOI: 10.1002/pro.4011] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2020] [Revised: 11/21/2020] [Accepted: 12/06/2020] [Indexed: 12/13/2022]
Abstract
Experimental observations of enzymes under active turnover conditions have brought new insight into the role of protein motions and allosteric networks in catalysis. Many of these studies characterize enzymes under dynamic chemical equilibrium conditions, in which the enzyme is actively catalyzing both the forward and reverse reactions during data acquisition. We have previously analyzed conformational dynamics and allosteric networks of the alpha subunit of tryptophan synthase under such conditions using NMR. We have proposed that this working state represents a four to one ratio of the enzyme bound with the indole-3-glycerol phosphate substrate (E:IGP) to the enzyme bound with the products indole and glyceraldehyde-3-phosphate (E:indole:G3P). Here, we analyze the inactive D60N variant to deconvolute the contributions of the substrate- and products-bound states to the working state. While the D60N substitution itself induces small structural and dynamic changes, the D60N E:IGP and E:indole:G3P states cannot entirely account for the conformational dynamics and allosteric networks present in the working state. The act of chemical bond breakage and/or formation, or possibly the generation of an intermediate, may alter the structure and dynamics present in the working state. As the enzyme transitions from the substrate-bound to the products-bound state, millisecond conformational exchange processes are quenched and new allosteric connections are made between the alpha active site and the surface which interfaces with the beta subunit. The structural ordering of the enzyme and these new allosteric connections may be important in coordinating the channeling of the indole product into the beta subunit.
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Affiliation(s)
- Kathleen F O'Rourke
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Rebecca N D'Amico
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Debashish Sahu
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - David D Boehr
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania, USA
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4
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Steinmann C, Bratholm LA, Olsen JMH, Kongsted J. Automated Fragmentation Polarizable Embedding Density Functional Theory (PE-DFT) Calculations of Nuclear Magnetic Resonance (NMR) Shielding Constants of Proteins with Application to Chemical Shift Predictions. J Chem Theory Comput 2017; 13:525-536. [PMID: 27992211 DOI: 10.1021/acs.jctc.6b00965] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Full-protein nuclear magnetic resonance (NMR) shielding constants based on ab initio calculations are desirable, because they can assist in elucidating protein structures from NMR experiments. In this work, we present NMR shielding constants computed using a new automated fragmentation (J. Phys. Chem. B 2009, 113, 10380-10388) approach in the framework of polarizable embedding density functional theory. We extend our previous work to give both basis set recommendations and comment on how large the quantum mechanical region should be to successfully compute 13C NMR shielding constants that are comparable with experiment. The introduction of a probabilistic linear regression model allows us to substantially reduce the number of snapshots that are needed to make comparisons with experiment. This approach is further improved by augmenting snapshot selection with chemical shift predictions by which we can obtain a representative subset of snapshots that gives the smallest predicted error, compared to experiment. Finally, we use this subset of snapshots to calculate the NMR shielding constants at the PE-KT3/pcSseg-2 level of theory for all atoms in the protein GB3.
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Affiliation(s)
- Casper Steinmann
- Centre for Computational Chemistry, School of Chemistry, University of Bristol , Bristol BS8 1TS, United Kingdom.,Department of Physics, Chemistry and Pharmacy, University of Southern Denmark , DK-5230 Odense M, Denmark
| | | | | | - Jacob Kongsted
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark , DK-5230 Odense M, Denmark
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5
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Quinn CM, Polenova T. Structural biology of supramolecular assemblies by magic-angle spinning NMR spectroscopy. Q Rev Biophys 2017; 50:e1. [PMID: 28093096 PMCID: PMC5483179 DOI: 10.1017/s0033583516000159] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
In recent years, exciting developments in instrument technology and experimental methodology have advanced the field of magic-angle spinning (MAS) nuclear magnetic resonance (NMR) to new heights. Contemporary MAS NMR yields atomic-level insights into structure and dynamics of an astounding range of biological systems, many of which cannot be studied by other methods. With the advent of fast MAS, proton detection, and novel pulse sequences, large supramolecular assemblies, such as cytoskeletal proteins and intact viruses, are now accessible for detailed analysis. In this review, we will discuss the current MAS NMR methodologies that enable characterization of complex biomolecular systems and will present examples of applications to several classes of assemblies comprising bacterial and mammalian cytoskeleton as well as human immunodeficiency virus 1 and bacteriophage viruses. The body of work reviewed herein is representative of the recent advancements in the field, with respect to the complexity of the systems studied, the quality of the data, and the significance to the biology.
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Affiliation(s)
- Caitlin M. Quinn
- University of Delaware, Department of Chemistry and Biochemistry, Newark, DE 19711; Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15306
| | - Tatyana Polenova
- University of Delaware, Department of Chemistry and Biochemistry, Newark, DE 19711; Pittsburgh Center for HIV Protein Interactions, University of Pittsburgh School of Medicine, Pittsburgh, PA 15306
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6
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Caulkins BG, Young RP, Kudla RA, Yang C, Bittbauer T, Bastin B, Hilario E, Fan L, Marsella MJ, Dunn MF, Mueller LJ. NMR Crystallography of a Carbanionic Intermediate in Tryptophan Synthase: Chemical Structure, Tautomerization, and Reaction Specificity. J Am Chem Soc 2016; 138:15214-15226. [PMID: 27779384 PMCID: PMC5129030 DOI: 10.1021/jacs.6b08937] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Indexed: 12/22/2022]
Abstract
Carbanionic intermediates play a central role in the catalytic transformations of amino acids performed by pyridoxal-5'-phosphate (PLP)-dependent enzymes. Here, we make use of NMR crystallography-the synergistic combination of solid-state nuclear magnetic resonance, X-ray crystallography, and computational chemistry-to interrogate a carbanionic/quinonoid intermediate analogue in the β-subunit active site of the PLP-requiring enzyme tryptophan synthase. The solid-state NMR chemical shifts of the PLP pyridine ring nitrogen and additional sites, coupled with first-principles computational models, allow a detailed model of protonation states for ionizable groups on the cofactor, substrates, and nearby catalytic residues to be established. Most significantly, we find that a deprotonated pyridine nitrogen on PLP precludes formation of a true quinonoid species and that there is an equilibrium between the phenolic and protonated Schiff base tautomeric forms of this intermediate. Natural bond orbital analysis indicates that the latter builds up negative charge at the substrate Cα and positive charge at C4' of the cofactor, consistent with its role as the catalytic tautomer. These findings support the hypothesis that the specificity for β-elimination/replacement versus transamination is dictated in part by the protonation states of ionizable groups on PLP and the reacting substrates and underscore the essential role that NMR crystallography can play in characterizing both chemical structure and dynamics within functioning enzyme active sites.
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Affiliation(s)
- Bethany G. Caulkins
- Department of Chemistry, and Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Robert P. Young
- Department of Chemistry, and Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Ryan A. Kudla
- Department of Chemistry, and Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Chen Yang
- Department of Chemistry, and Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Thomas
J. Bittbauer
- Department of Chemistry, and Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Baback Bastin
- Department of Chemistry, and Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Eduardo Hilario
- Department of Chemistry, and Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Li Fan
- Department of Chemistry, and Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Michael J. Marsella
- Department of Chemistry, and Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Michael F. Dunn
- Department of Chemistry, and Department of Biochemistry, University of California, Riverside, California 92521, United States
| | - Leonard J. Mueller
- Department of Chemistry, and Department of Biochemistry, University of California, Riverside, California 92521, United States
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7
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Huang YMM, You W, Caulkins BG, Dunn MF, Mueller LJ, Chang CEA. Protonation states and catalysis: Molecular dynamics studies of intermediates in tryptophan synthase. Protein Sci 2015; 25:166-83. [PMID: 26013176 DOI: 10.1002/pro.2709] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 05/13/2015] [Accepted: 05/14/2015] [Indexed: 12/13/2022]
Abstract
The importance of protonation states and proton transfer in pyridoxal 5'-phosphate (PLP)-chemistry can hardly be overstated. Although experimental approaches to investigate pKa values can provide general guidance for assigning proton locations, only static pictures of the chemical species are available. To obtain the overall protein dynamics for the interpretation of detailed enzyme catalysis in this study, guided by information from solid-state NMR, we performed molecular dynamics (MD) simulations for the PLP-dependent enzyme tryptophan synthase (TRPS), whose catalytic mechanism features multiple quasi-stable intermediates. The primary objective of this work is to elucidate how the position of a single proton on the reacting substrate affects local and global protein dynamics during the catalytic cycle. In general, proteins create a chemical environment and an ensemble of conformational motions to recognize different substrates with different protonations. The study of these interactions in TRPS shows that functional groups on the reacting substrate, such as the phosphoryl group, pyridine nitrogen, phenolic oxygen and carboxyl group, of each PLP-bound intermediate play a crucial role in constructing an appropriate molecular interface with TRPS. In particular, the protonation states of the ionizable groups on the PLP cofactor may enhance or weaken the attractions between the enzyme and substrate. In addition, remodulation of the charge distribution for the intermediates may help generate a suitable environment for chemical reactions. The results of our study enhance knowledge of protonation states for several PLP intermediates and help to elucidate their effects on protein dynamics in the function of TRPS and other PLP-dependent enzymes.
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Affiliation(s)
- Yu-Ming M Huang
- Department of Chemistry, University of California, Riverside, California, 92521
| | - Wanli You
- Department of Chemistry, University of California, Riverside, California, 92521
| | - Bethany G Caulkins
- Department of Chemistry, University of California, Riverside, California, 92521
| | - Michael F Dunn
- Department of Biochemistry, University of California, Riverside, California, 92521
| | - Leonard J Mueller
- Department of Chemistry, University of California, Riverside, California, 92521
| | - Chia-En A Chang
- Department of Chemistry, University of California, Riverside, California, 92521
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8
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Hartman JD, Neubauer TJ, Caulkins BG, Mueller LJ, Beran GJO. Converging nuclear magnetic shielding calculations with respect to basis and system size in protein systems. JOURNAL OF BIOMOLECULAR NMR 2015; 62:327-40. [PMID: 25993979 PMCID: PMC4512207 DOI: 10.1007/s10858-015-9947-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 05/12/2015] [Indexed: 05/25/2023]
Abstract
Ab initio chemical shielding calculations greatly facilitate the interpretation of nuclear magnetic resonance (NMR) chemical shifts in biological systems, but the large sizes of these systems requires approximations in the chemical models used to represent them. Achieving good convergence in the predicted chemical shieldings is necessary before one can unravel how other complex structural and dynamical factors affect the NMR measurements. Here, we investigate how to balance trade-offs between using a better basis set or a larger cluster model for predicting the chemical shieldings of the substrates in two representative examples of protein-substrate systems involving different domains in tryptophan synthase: the N-(4'-trifluoromethoxybenzoyl)-2-aminoethyl phosphate (F9) ligand which binds in the α active site, and the 2-aminophenol quinonoid intermediate formed in the β active site. We first demonstrate that a chemically intuitive three-layer, locally dense basis model that uses a large basis on the substrate, a medium triple-zeta basis to describe its hydrogen-bonding partners and/or surrounding van der Waals cavity, and a crude basis set for more distant atoms provides chemical shieldings in good agreement with much more expensive large basis calculations. Second, long-range quantum mechanical interactions are important, and one can accurately estimate them as a small-basis correction to larger-basis calculations on a smaller cluster. The combination of these approaches enables one to perform density functional theory NMR chemical shift calculations in protein systems that are well-converged with respect to both basis set and cluster size.
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Affiliation(s)
- Joshua D. Hartman
- Department of Chemistry, University of California at Riverside, Riverside, CA 92521, Tel.: +1-951-827-7869
| | - Thomas J. Neubauer
- Department of Chemistry, University of California at Riverside, Riverside, CA 92521, Tel.: +1-951-827-7869
| | - Bethany G. Caulkins
- Department of Chemistry, University of California at Riverside, Riverside, CA 92521, Tel.: +1-951-827-7869
| | - Leonard J. Mueller
- Department of Chemistry, University of California at Riverside, Riverside, CA 92521, Tel.: +1-951-827-7869
| | - Gregory J. O. Beran
- Department of Chemistry, University of California at Riverside, Riverside, CA 92521, Tel.: +1-951-827-7869
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9
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Mozzarelli A, Pollegioni L. Special Issue on "Cofactor-dependent proteins: Evolution, chemical diversity and bio-applications". BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1854:1071-2. [PMID: 26071224 DOI: 10.1016/j.bbapap.2015.06.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Andrea Mozzarelli
- Department of Pharmacy, University of Parma, Parma, Italy; National Institute of Biostructure and Biosystems, Rome, Italy; Institute of Biophysics, CNR, Pisa, Italy
| | - Loredano Pollegioni
- Department of Biotechnology and Life Sciences, University of Insubria, Varese, Italy; Protein Factory, InterUniversity Center for Protein Biotechnology, Politecnico di Milano, Università degli studi dell'Insubria and ICRM CNR Milano, Italy
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10
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Huang YMM, Kang M, Chang CEA. Switches of hydrogen bonds during ligand-protein association processes determine binding kinetics. J Mol Recognit 2015; 27:537-48. [PMID: 25042708 DOI: 10.1002/jmr.2377] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Revised: 03/22/2014] [Accepted: 03/24/2014] [Indexed: 11/05/2022]
Abstract
Revealing the processes of ligand-protein associations deepens our understanding of molecular recognition and binding kinetics. Hydrogen bonds (H-bonds) play a crucial role in optimizing ligand-protein interactions and ligand specificity. In addition to the formation of stable H-bonds in the final bound state, the formation of transient H-bonds during binding processes contributes binding kinetics that define a ligand as a fast or slow binder, which also affects drug action. However, the effect of forming the transient H-bonds on the kinetic properties is little understood. Guided by results from coarse-grained Brownian dynamics simulations, we used classical molecular dynamics simulations in an implicit solvent model and accelerated molecular dynamics simulations in explicit waters to show that the position and distribution of the H-bond donor or acceptor of a drug result in switching intermolecular and intramolecular H-bond pairs during ligand recognition processes. We studied two major types of HIV-1 protease ligands: a fast binder, xk263, and a slow binder, ritonavir. The slow association rate in ritonavir can be attributed to increased flexibility of ritonavir, which yields multistep transitions and stepwise entering patterns and the formation and breaking of complex H-bond pairs during the binding process. This model suggests the importance of conversions of spatiotemporal H-bonds during the association of ligands and proteins, which helps in designing inhibitors with preferred binding kinetics.
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Affiliation(s)
- Yu-ming M Huang
- Department of Chemistry, University of California, Riverside, CA, 92521, USA
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