1
|
Shenderovich IG. The Scope of the Applicability of Non-relativistic DFT Calculations of NMR Chemical Shifts in Pyridine-Metal Complexes for Applied Applications. Chemphyschem 2024; 25:e202300986. [PMID: 38259119 DOI: 10.1002/cphc.202300986] [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: 12/21/2023] [Revised: 01/23/2024] [Accepted: 01/23/2024] [Indexed: 01/24/2024]
Abstract
Heavy metals are toxic, but it is impossible to stop using them. Considering the variety of molecular systems in which they can be present, the multicomponent nature and disorder of the structure of such systems, one of the most effective methods for studying them is NMR spectroscopy. This determines the need to calculate NMR chemical shifts for expected model systems. For elements beyond the third row of the periodic table, corrections for relativistic effects are necessary when calculating NMR parameters. Such corrections may be necessary even for light atoms due to the shielding effect of a neighboring heavy atom. This work examines the extent to which non-relativistic DFT calculations are able to reproduce experimental 15N and 113Cd NMR chemical shift tensors in pyridine-metal coordination complexes. It is shown that while for the calculation of 15N NMR chemical shift tensors there is no real need to consider relativistic corrections, for 113Cd, on the contrary, none of the tested calculation methods could reproduce the experimentally obtained tensor to any extent correctly.
Collapse
Affiliation(s)
- Ilya G Shenderovich
- NMR Department, Faculty of Chemistry and Pharmacy, University of Regensburg, 93040, Regensburg, Germany
| |
Collapse
|
2
|
Wilson C, Karttunen M, de Groot BL, Gapsys V. Accurately Predicting Protein p Ka Values Using Nonequilibrium Alchemy. J Chem Theory Comput 2023; 19:7833-7845. [PMID: 37820376 PMCID: PMC10653114 DOI: 10.1021/acs.jctc.3c00721] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Indexed: 10/13/2023]
Abstract
The stability, solubility, and function of a protein depend on both its net charge and the protonation states of its individual residues. pKa is a measure of the tendency for a given residue to (de)protonate at a specific pH. Although pKa values can be resolved experimentally, theory and computation provide a compelling alternative. To this end, we assess the applicability of a nonequilibrium (NEQ) alchemical free energy method to the problem of pKa prediction. On a data set of 144 residues that span 13 proteins, we report an average unsigned error of 0.77 ± 0.09, 0.69 ± 0.09, and 0.52 ± 0.04 pK for aspartate, glutamate, and lysine, respectively. This is comparable to current state-of-the-art predictors and the accuracy recently reached using free energy perturbation methods (e.g., FEP+). Moreover, we demonstrate that our open-source, pmx-based approach can accurately resolve the pKa values of coupled residues and observe a substantial performance disparity associated with the lysine partial charges in Amber14SB/Amber99SB*-ILDN, for which an underused fix already exists.
Collapse
Affiliation(s)
- Carter
J. Wilson
- Department
of Mathematics, The University of Western
Ontario, N6A 5B7 London, Canada
- Centre
for Advanced Materials and Biomaterials Research (CAMBR), The University of Western Ontario, N6A 5B7 London, Canada
| | - Mikko Karttunen
- Centre
for Advanced Materials and Biomaterials Research (CAMBR), The University of Western Ontario, N6A 5B7 London, Canada
- Department
of Physics & Astronomy, The University
of Western Ontario, N6A
5B7 London, Canada
- Department
of Chemistry, The University of Western
Ontario, N6A 5B7 London, Canada
| | - Bert L. de Groot
- Computational
Biomolecular Dynamics Group, Department of Theoretical and Computational
Biophysics, Max Planck Institute for Multidisciplinary
Sciences, 37077 Göttingen, Germany
| | - Vytautas Gapsys
- Computational
Biomolecular Dynamics Group, Department of Theoretical and Computational
Biophysics, Max Planck Institute for Multidisciplinary
Sciences, 37077 Göttingen, Germany
- Computational
Chemistry, Janssen Research & Development, Janssen Pharmaceutica N. V., Turnhoutseweg 30, B-2340 Beerse, Belgium
| |
Collapse
|
3
|
Brüschweiler S, Fuchs JE, Bader G, McConnell DB, Konrat R, Mayer M. A Step toward NRF2-DNA Interaction Inhibitors by Fragment-Based NMR Methods. ChemMedChem 2021; 16:3576-3587. [PMID: 34524728 PMCID: PMC9293343 DOI: 10.1002/cmdc.202100458] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Revised: 08/30/2021] [Indexed: 12/30/2022]
Abstract
The NRF2 transcription factor is a key regulator in cellular oxidative stress response, and acts as a tumor suppressor. Aberrant activation of NRF2 has been implicated in promoting chemo-resistance, tumor growth, and metastasis by activating its downstream target genes. Hence, inhibition of NRF2 promises to be an attractive therapeutic strategy to suppress cell proliferation and enhance cell apoptosis in cancer. Direct targeting of NRF2 with small-molecules to discover protein-DNA interaction inhibitors is challenging as it is a largely intrinsically disordered protein. To discover molecules that bind to NRF2 at the DNA binding interface, we performed an NMR-based fragment screen against its DNA-binding domain. We discovered several weakly binding fragment hits that bind to a region overlapping with the DNA binding site. Using SAR by catalogue we developed an initial structure-activity relationship for the most interesting initial hit series. By combining NMR chemical shift perturbations and data-driven docking, binding poses which agreed with NMR information and the observed SAR were elucidated. The herein discovered NRF2 hits and proposed binding modes form the basis for future structure-based optimization campaigns on this important but to date 'undrugged' cancer driver.
Collapse
Affiliation(s)
- Sven Brüschweiler
- Christian Doppler Laboratory for High-Content Structural Biology and BiotechnologyDepartment of Structural and Computational Biology, Max Perutz LabsUniversity of ViennaCampus Vienna Biocenter 51030ViennaAustria
| | - Julian E. Fuchs
- Boehringer Ingelheim RCV GmbH & Co. KGDr. Boehringer Gasse 5–111121ViennaAustria
| | - Gerd Bader
- Boehringer Ingelheim RCV GmbH & Co. KGDr. Boehringer Gasse 5–111121ViennaAustria
| | - Darryl B. McConnell
- Boehringer Ingelheim RCV GmbH & Co. KGDr. Boehringer Gasse 5–111121ViennaAustria
| | - Robert Konrat
- Christian Doppler Laboratory for High-Content Structural Biology and BiotechnologyDepartment of Structural and Computational Biology, Max Perutz LabsUniversity of ViennaCampus Vienna Biocenter 51030ViennaAustria
| | - Moriz Mayer
- Boehringer Ingelheim RCV GmbH & Co. KGDr. Boehringer Gasse 5–111121ViennaAustria
| |
Collapse
|
4
|
NMR spectroscopy charges into protein surface electrostatics. Proc Natl Acad Sci U S A 2021; 118:2110176118. [PMID: 34301877 DOI: 10.1073/pnas.2110176118] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
5
|
Artikis E, Brooks CL. Modeling pH-Dependent NMR Chemical Shift Perturbations in Peptides. Biophys J 2019; 117:258-268. [PMID: 31255294 DOI: 10.1016/j.bpj.2019.06.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 04/20/2019] [Accepted: 06/03/2019] [Indexed: 11/29/2022] Open
Abstract
Modeling the pH dependence of protein and peptide chemical shifts outside the range of physiological values (6.5-7) is key to understanding structure-function relationships of these systems. These capabilities are largely not available in current chemical shift prediction software. In this study, we utilize a combination of molecular dynamics and quantum mechanics to investigate the through-space and through-bond contributions of protonation-dependent chemical shift perturbations (CSPs) in model tripeptides. By altering the protonation state of the titratable group in the tripeptides, we observe a notable difference in the conformational ensembles and attendantly compute significant CSPs for all nuclei near the site of protonation. We thus demonstrate the ability to recapitulate experimental pH-dependent CSPs with good agreement (R = 0.85, 0.99, and 0.98 for 13C, 15N, and 1H, respectively). Broadly, we provide the groundwork for incorporating pH effects into empirical and semiempirical chemical shift predictors.
Collapse
Affiliation(s)
| | - Charles L Brooks
- Biophysics Program, University of Michigan, Ann Arbor, Michigan; Department of Chemistry, University of Michigan, Ann Arbor, Michigan.
| |
Collapse
|
6
|
Wahle CW, Martini KM, Hollenbeck DM, Langner A, Ross DS, Hamilton JF, Thurston GM. Model for screened, charge-regulated electrostatics of an eye lens protein: Bovine gammaB-crystallin. Phys Rev E 2017; 96:032415. [PMID: 29346981 PMCID: PMC5830141 DOI: 10.1103/physreve.96.032415] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Indexed: 06/07/2023]
Abstract
We model screened, site-specific charge regulation of the eye lens protein bovine gammaB-crystallin (γB) and study the probability distributions of its proton occupancy patterns. Using a simplified dielectric model, we solve the linearized Poisson-Boltzmann equation to calculate a 54×54 work-of-charging matrix, each entry being the modeled voltage at a given titratable site, due to an elementary charge at another site. The matrix quantifies interactions within patches of sites, including γB charge pairs. We model intrinsic pK values that would occur hypothetically in the absence of other charges, with use of experimental data on the dependence of pK values on aqueous solution conditions, the dielectric model, and literature values. We use Monte Carlo simulations to calculate a model grand-canonical partition function that incorporates both the work-of-charging and the intrinsic pK values for isolated γB molecules and we calculate the probabilities of leading proton occupancy configurations, for 4<pH<8 and Debye screening lengths from 6 to 20 Å. We select the interior dielectric value to model γB titration data. At pH 7.1 and Debye length 6.0 Å, on a given γB molecule the predicted top occupancy pattern is present nearly 20% of the time, and 90% of the time one or another of the first 100 patterns will be present. Many of these occupancy patterns differ in net charge sign as well as in surface voltage profile. We illustrate how charge pattern probabilities deviate from the multinomial distribution that would result from use of effective pK values alone and estimate the extents to which γB charge pattern distributions broaden at lower pH and narrow as ionic strength is lowered. These results suggest that for accurate modeling of orientation-dependent γB-γB interactions, consideration of numerous pairs of proton occupancy patterns will be needed.
Collapse
Affiliation(s)
- Christopher W. Wahle
- School of Mathematical Sciences, Rochester Institute of Technology, Rochester, New York 14623, USA
| | - K. Michael Martini
- School of Physics and Astronomy, Rochester Institute of Technology, Rochester, New York 14623, USA
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana-Champaign, Illinois 61801, USA
| | - Dawn M. Hollenbeck
- School of Physics and Astronomy, Rochester Institute of Technology, Rochester, New York 14623, USA
| | - Andreas Langner
- School of Chemistry and Materials Science, Rochester Institute of Technology, Rochester, New York 14623, USA
| | - David S. Ross
- School of Mathematical Sciences, Rochester Institute of Technology, Rochester, New York 14623, USA
| | - John F. Hamilton
- School of Mathematical Sciences, Rochester Institute of Technology, Rochester, New York 14623, USA
| | - George M. Thurston
- School of Physics and Astronomy, Rochester Institute of Technology, Rochester, New York 14623, USA
| |
Collapse
|
7
|
Abriata LA, Spiga E, Peraro MD. Molecular Effects of Concentrated Solutes on Protein Hydration, Dynamics, and Electrostatics. Biophys J 2017; 111:743-755. [PMID: 27558718 DOI: 10.1016/j.bpj.2016.07.011] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 06/06/2016] [Accepted: 07/05/2016] [Indexed: 12/20/2022] Open
Abstract
Most studies of protein structure and function are performed in dilute conditions, but proteins typically experience high solute concentrations in their physiological scenarios and biotechnological applications. High solute concentrations have well-known effects on coarse protein traits like stability, diffusion, and shape, but likely also perturb other traits through finer effects pertinent at the residue and atomic levels. Here, NMR and molecular dynamics investigations on ubiquitin disclose variable interactions with concentrated solutes that lead to localized perturbations of the protein's surface, hydration, electrostatics, and dynamics, all dependent on solute size and chemical properties. Most strikingly, small polar uncharged molecules are sticky on the protein surface, whereas charged small molecules are not, but the latter still perturb the internal protein electrostatics as they diffuse nearby. Meanwhile, interactions with macromolecular crowders are favored mainly through hydrophobic, but not through polar, surface patches. All the tested small solutes strongly slow down water exchange at the protein surface, whereas macromolecular crowders do not exert such strong perturbation. Finally, molecular dynamics simulations predict that unspecific interactions slow down microsecond- to millisecond-timescale protein dynamics despite having only mild effects on pico- to nanosecond fluctuations as corroborated by NMR. We discuss our results in the light of recent advances in understanding proteins inside living cells, focusing on the physical chemistry of quinary structure and cellular organization, and we reinforce the idea that proteins should be studied in native-like media to achieve a faithful description of their function.
Collapse
Affiliation(s)
- Luciano A Abriata
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne and Swiss Institute of Bioinformatics, Lausanne, Switzerland.
| | - Enrico Spiga
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne and Swiss Institute of Bioinformatics, Lausanne, Switzerland
| | - Matteo Dal Peraro
- Institute of Bioengineering, School of Life Sciences, École Polytechnique Fédérale de Lausanne and Swiss Institute of Bioinformatics, Lausanne, Switzerland.
| |
Collapse
|
8
|
Zhang N, An L, Li J, Liu Z, Yao L. Quinary Interactions Weaken the Electric Field Generated by Protein Side-Chain Charges in the Cell-like Environment. J Am Chem Soc 2017; 139:647-654. [DOI: 10.1021/jacs.6b11058] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Ning Zhang
- University of Chinese Academy of Sciences, Beijing 100049, China
| | | | - Jingwen Li
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhijun Liu
- National
Center for Protein Science Shanghai, Institute of Biochemistry and
Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 201210, China
| | | |
Collapse
|
9
|
Gandhi NS, Kukic P, Lippens G, Mancera RL. Molecular Dynamics Simulation of Tau Peptides for the Investigation of Conformational Changes Induced by Specific Phosphorylation Patterns. Methods Mol Biol 2017; 1523:33-59. [PMID: 27975243 DOI: 10.1007/978-1-4939-6598-4_3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The Tau protein plays an important role due to its biomolecular interactions in neurodegenerative diseases. The lack of stable structure and various posttranslational modifications such as phosphorylation at various sites in the Tau protein pose a challenge for many experimental methods that are traditionally used to study protein folding and aggregation. Atomistic molecular dynamics (MD) simulations can help around deciphering relationship between phosphorylation and various intermediate and stable conformations of the Tau protein which occur on longer timescales. This chapter outlines protocols for the preparation, execution, and analysis of all-atom MD simulations of a 21-amino acid-long phosphorylated Tau peptide with the aim of generating biologically relevant structural and dynamic information. The simulations are done in explicit solvent and starting from nearly extended configurations of the peptide. The scaled MD method implemented in AMBER14 was chosen to achieve enhanced conformational sampling in addition to a conventional MD approach, thereby allowing the characterization of folding for such an intrinsically disordered peptide at 293 K. Emphasis is placed on the analysis of the simulation trajectories to establish correlations with NMR data (i.e., chemical shifts and NOEs). Finally, in-depth discussions are provided for commonly encountered problems.
Collapse
Affiliation(s)
- Neha S Gandhi
- School of Biomedical Sciences, CHIRI Biosciences and Curtin Institute for Computation, Curtin University, G.P.O. Box U1987, Perth, WA, 6845, Australia.
| | - Predrag Kukic
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK
| | - Guy Lippens
- Laboratoire d'Ingénierie des Systèmes Biologiques et des Procédés, Université de Toulouse, CNRS, INRA, INSA Toulouse, 135Avenue de Rangueil, 31077, Toulouse, France
- Université de Lille, CNRS, UMR 8576, UGSF-Unité de Glycobiologie Structurale et Fonctionnelle, 59000 Lille, France
| | - Ricardo L Mancera
- School of Biomedical Sciences, CHIRI Biosciences and Curtin Institute for Computation, Curtin University, G.P.O. Box U1987, Perth, WA, 6845, Australia.
| |
Collapse
|
10
|
Conformational Dynamics and Binding Free Energies of Inhibitors of BACE-1: From the Perspective of Protonation Equilibria. PLoS Comput Biol 2015; 11:e1004341. [PMID: 26506513 PMCID: PMC4623973 DOI: 10.1371/journal.pcbi.1004341] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2015] [Accepted: 05/17/2015] [Indexed: 11/19/2022] Open
Abstract
BACE-1 is the β-secretase responsible for the initial amyloidogenesis in Alzheimer’s disease, catalyzing hydrolytic cleavage of substrate in a pH-sensitive manner. The catalytic mechanism of BACE-1 requires water-mediated proton transfer from aspartyl dyad to the substrate, as well as structural flexibility in the flap region. Thus, the coupling of protonation and conformational equilibria is essential to a full in silico characterization of BACE-1. In this work, we perform constant pH replica exchange molecular dynamics simulations on both apo BACE-1 and five BACE-1-inhibitor complexes to examine the effect of pH on dynamics and inhibitor binding properties of BACE-1. In our simulations, we find that solution pH controls the conformational flexibility of apo BACE-1, whereas bound inhibitors largely limit the motions of the holo enzyme at all levels of pH. The microscopic pKa values of titratable residues in BACE-1 including its aspartyl dyad are computed and compared between apo and inhibitor-bound states. Changes in protonation between the apo and holo forms suggest a thermodynamic linkage between binding of inhibitors and protons localized at the dyad. Utilizing our recently developed computational protocol applying the binding polynomial formalism to the constant pH molecular dynamics (CpHMD) framework, we are able to obtain the pH-dependent binding free energy profiles for various BACE-1-inhibitor complexes. Our results highlight the importance of correctly addressing the binding-induced protonation changes in protein-ligand systems where binding accompanies a net proton transfer. This work comprises the first application of our CpHMD-based free energy computational method to protein-ligand complexes and illustrates the value of CpHMD as an all-purpose tool for obtaining pH-dependent dynamics and binding free energies of biological systems. Formation of insoluble amyloid plaques in the vascular and hippocampal areas of the brain characterizes Alzheimer’s disease, a devastating neurodegenerative disorder causing dementia. Site-specific hydrolytic catalysis of β-secretase, or BACE-1, is responsible for production of oligomerative amyloid β-peptide. As the catalytic activity of BACE-1 is pH-dependent and its structural dynamics are intrinsic to the catalysis, we examine the dependence of dynamics of BACE-1 on solution pH and its implications on the catalytic mechanism of BACE-1. Also, we highlight the importance of accurate description of protonation states of the titratable groups in computer-aided drug discovery targeting BACE-1. We hope the understanding of pH dependence of the dynamics and inhibitor binding properties of BACE-1 will aid the structure-based inhibitor design efforts against Alzheimer’s disease.
Collapse
|
11
|
Affiliation(s)
- Mathias A.S. Hass
- Institute of Chemistry, Gorlaeus Laboratories, Leiden University, 2300 RA Leiden, The Netherlands
| | - Frans A.A. Mulder
- Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C, Denmark;
| |
Collapse
|
12
|
Barb AW. Intramolecular N-glycan/polypeptide interactions observed at multiple N-glycan remodeling steps through [(13)C,(15)N]-N-acetylglucosamine labeling of immunoglobulin G1. Biochemistry 2014; 54:313-22. [PMID: 25551295 PMCID: PMC4302832 DOI: 10.1021/bi501380t] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
![]()
Asparagine-linked (N) glycosylation
is a common eukaryotic protein
modification that affects protein folding, function, and stability
through intramolecular interactions between N-glycan
and polypeptide residues. Attempts to characterize the structure–activity
relationship of each N-glycan are hindered by inherent
properties of the glycoprotein, including glycan conformational and
compositional heterogeneity. These limitations can be addressed by
using a combination of nuclear magnetic resonance techniques following
enzymatic glycan remodeling to simultaneously generate homogeneous
glycoforms. However, widely applicable methods do not yet exist. To
address this technological gap, immature glycoforms of the immunoglobulin
G1 fragment crystallizable (Fc) were isolated in a homogeneous state
and enzymatically remodeled with [13C,15N]-N-acetylglucosamine (GlcNAc). UDP-[13C,15N]GlcNAc was synthesized enzymatically in a one-pot reaction from
[13C]glucose and [15N-amido]glutamine. Modifying Fc with recombinantly expressed glycosyltransferases
(Gnt1 and Gnt2) and UDP-[13C,15N]GlcNAc resulted
in complete glycoform conversion as judged by mass spectrometry. Two-dimensional
heteronuclear single-quantum coherence spectra of the Gnt1 product,
containing a single [13C,15N]GlcNAc residue
on each N-glycan, showed that the N-glycan is stabilized through interactions with polypeptide residues.
Similar spectra of homogeneous glycoforms, halted at different points
along the N-glycan remodeling pathway, revealed the
presence of an increased level of interaction between the N-glycan and polypeptide at each step, including mannose
trimming, as the N-glycan was converted to a complex-type,
biantennary form. Thus, conformational restriction increases as Fc N-glycan maturation proceeds. Gnt1 and Gnt2 catalyze fundamental
reactions in the synthesis of every glycoprotein with a complex-type N-glycan; thus, the strategies presented herein can be applied
to a broad range of glycoprotein studies.
Collapse
Affiliation(s)
- Adam W Barb
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University , Ames, Iowa 50011, United States
| |
Collapse
|
13
|
Platzer G, Okon M, McIntosh LP. pH-dependent random coil (1)H, (13)C, and (15)N chemical shifts of the ionizable amino acids: a guide for protein pK a measurements. JOURNAL OF BIOMOLECULAR NMR 2014; 60:109-129. [PMID: 25239571 DOI: 10.1007/s10858-014-9862-y] [Citation(s) in RCA: 149] [Impact Index Per Article: 14.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 09/09/2014] [Indexed: 06/03/2023]
Abstract
The pK a values and charge states of ionizable residues in polypeptides and proteins are frequently determined via NMR-monitored pH titrations. To aid the interpretation of the resulting titration data, we have measured the pH-dependent chemical shifts of nearly all the (1)H, (13)C, and (15)N nuclei in the seven common ionizable amino acids (X = Asp, Glu, His, Cys, Tyr, Lys, and Arg) within the context of a blocked tripeptide, acetyl-Gly-X-Gly-amide. Alanine amide and N-acetyl alanine were used as models of the N- and C-termini, respectively. Together, this study provides an essentially complete set of pH-dependent intra-residue and nearest-neighbor reference chemical shifts to help guide protein pK a measurements. These data should also facilitate pH-dependent corrections in algorithms used to predict the chemical shifts of random coil polypeptides. In parallel, deuterium isotope shifts for the side chain (15)N nuclei of His, Lys, and Arg in their positively-charged and neutral states were also measured. Along with previously published results for Asp, Glu, Cys, and Tyr, these deuterium isotope shifts can provide complementary experimental evidence for defining the ionization states of protein residues.
Collapse
Affiliation(s)
- Gerald Platzer
- Department of Biochemistry and Molecular Biology, Life Sciences Centre, 2350 Health Sciences Mall, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada
| | | | | |
Collapse
|
14
|
An L, Wang Y, Zhang N, Yan S, Bax A, Yao L. Protein apparent dielectric constant and its temperature dependence from remote chemical shift effects. J Am Chem Soc 2014; 136:12816-9. [PMID: 25192058 PMCID: PMC4183759 DOI: 10.1021/ja505852b] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
A NMR protocol is introduced that
permits accurate measurement
of minute, remote chemical shift perturbations (CSPs), caused by a
mutation-induced change in the electric field. Using protein GB3 as
a model system, 1HN CSPs in K19A and K19E mutants
can be fitted to small changes in the electric field at distal sites
in the protein using the Buckingham equation, yielding an apparent
dielectric constant εa of 8.6 ± 0.8 at 298 K.
These CSPs, and their derived εa value, scale strongly
with temperature. For example, CSPs at 313 K are about ∼30%
smaller than those at 278 K, corresponding to an effective εa value of about 7.3 at 278 K and 10.5 at 313 K. Molecular
dynamics simulations in explicit solvent indicate that solvent water
makes a significant contribution to εa.
Collapse
Affiliation(s)
- Liaoyuan An
- Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences , Qingdao, 266101, China
| | | | | | | | | | | |
Collapse
|
15
|
Cao Z, Bowie JU. An energetic scale for equilibrium H/D fractionation factors illuminates hydrogen bond free energies in proteins. Protein Sci 2014; 23:566-75. [PMID: 24501090 DOI: 10.1002/pro.2435] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Revised: 01/29/2014] [Accepted: 01/29/2014] [Indexed: 11/09/2022]
Abstract
Equilibrium H/D fractionation factors have been extensively employed to qualitatively assess hydrogen bond strengths in protein structure, enzyme active sites, and DNA. It remains unclear how fractionation factors correlate with hydrogen bond free energies, however. Here we develop an empirical relationship between fractionation factors and free energy, allowing for the simple and quantitative measurement of hydrogen bond free energies. Applying our empirical relationship to prior fractionation factor studies in proteins, we find: [1] Within the folded state, backbone hydrogen bonds are only marginally stronger on average in α-helices compared to β-sheets by ∼0.2 kcal/mol. [2] Charge-stabilized hydrogen bonds are stronger than neutral hydrogen bonds by ∼2 kcal/mol on average, and can be as strong as -7 kcal/mol. [3] Changes in a few hydrogen bonds during an enzyme catalytic cycle can stabilize an intermediate state by -4.2 kcal/mol. [4] Backbone hydrogen bonds can make a large overall contribution to the energetics of conformational changes, possibly playing an important role in directing conformational changes. [5] Backbone hydrogen bonding becomes more uniform overall upon ligand binding, which may facilitate participation of the entire protein structure in events at the active site. Our energetic scale provides a simple method for further exploration of hydrogen bond free energies.
Collapse
Affiliation(s)
- Zheng Cao
- Department of Chemistry and Biochemistry, UCLA-DOE Institute for Genomics and Proteomics and the Molecular Biology Institute, University of California, Los Angeles, California
| | | |
Collapse
|
16
|
Kukic P, Farrell D, McIntosh LP, García-Moreno E B, Jensen KS, Toleikis Z, Teilum K, Nielsen JE. Protein dielectric constants determined from NMR chemical shift perturbations. J Am Chem Soc 2013; 135:16968-76. [PMID: 24124752 DOI: 10.1021/ja406995j] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Understanding the connection between protein structure and function requires a quantitative understanding of electrostatic effects. Structure-based electrostatic calculations are essential for this purpose, but their use has been limited by a long-standing discussion on which value to use for the dielectric constants (ε(eff) and ε(p)) required in Coulombic and Poisson-Boltzmann models. The currently used values for ε(eff) and ε(p) are essentially empirical parameters calibrated against thermodynamic properties that are indirect measurements of protein electric fields. We determine optimal values for ε(eff) and ε(p) by measuring protein electric fields in solution using direct detection of NMR chemical shift perturbations (CSPs). We measured CSPs in 14 proteins to get a broad and general characterization of electric fields. Coulomb's law reproduces the measured CSPs optimally with a protein dielectric constant (ε(eff)) from 3 to 13, with an optimal value across all proteins of 6.5. However, when the water-protein interface is treated with finite difference Poisson-Boltzmann calculations, the optimal protein dielectric constant (ε(p)) ranged from 2 to 5 with an optimum of 3. It is striking how similar this value is to the dielectric constant of 2-4 measured for protein powders and how different it is from the ε(p) of 6-20 used in models based on the Poisson-Boltzmann equation when calculating thermodynamic parameters. Because the value of ε(p) = 3 is obtained by analysis of NMR chemical shift perturbations instead of thermodynamic parameters such as pK(a) values, it is likely to describe only the electric field and thus represent a more general, intrinsic, and transferable ε(p) common to most folded proteins.
Collapse
Affiliation(s)
- Predrag Kukic
- School of Biomolecular and Biomedical Science, Centre for Synthesis and Chemical Biology, UCD Conway Institute, University College Dublin , Belfield, Dublin 4, Ireland
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Williamson MP. Using chemical shift perturbation to characterise ligand binding. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2013; 73:1-16. [PMID: 23962882 DOI: 10.1016/j.pnmrs.2013.02.001] [Citation(s) in RCA: 956] [Impact Index Per Article: 86.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2013] [Revised: 02/12/2013] [Accepted: 02/18/2013] [Indexed: 05/05/2023]
Abstract
Chemical shift perturbation (CSP, chemical shift mapping or complexation-induced changes in chemical shift, CIS) follows changes in the chemical shifts of a protein when a ligand is added, and uses these to determine the location of the binding site, the affinity of the ligand, and/or possibly the structure of the complex. A key factor in determining the appearance of spectra during a titration is the exchange rate between free and bound, or more specifically the off-rate koff. When koff is greater than the chemical shift difference between free and bound, which typically equates to an affinity Kd weaker than about 3μM, then exchange is fast on the chemical shift timescale. Under these circumstances, the observed shift is the population-weighted average of free and bound, which allows Kd to be determined from measurement of peak positions, provided the measurements are made appropriately. (1)H shifts are influenced to a large extent by through-space interactions, whereas (13)Cα and (13)Cβ shifts are influenced more by through-bond effects. (15)N and (13)C' shifts are influenced both by through-bond and by through-space (hydrogen bonding) interactions. For determining the location of a bound ligand on the basis of shift change, the most appropriate method is therefore usually to measure (15)N HSQC spectra, calculate the geometrical distance moved by the peak, weighting (15)N shifts by a factor of about 0.14 compared to (1)H shifts, and select those residues for which the weighted shift change is larger than the standard deviation of the shift for all residues. Other methods are discussed, in particular the measurement of (13)CH3 signals. Slow to intermediate exchange rates lead to line broadening, and make Kd values very difficult to obtain. There is no good way to distinguish changes in chemical shift due to direct binding of the ligand from changes in chemical shift due to allosteric change. Ligand binding at multiple sites can often be characterised, by simultaneous fitting of many measured shift changes, or more simply by adding substoichiometric amounts of ligand. The chemical shift changes can be used as restraints for docking ligand onto protein. By use of quantitative calculations of ligand-induced chemical shift changes, it is becoming possible to determine not just the position but also the orientation of ligands.
Collapse
Affiliation(s)
- Mike P Williamson
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK.
| |
Collapse
|
18
|
Nielsen G, Jonker HRA, Vajpai N, Grzesiek S, Schwalbe H. Kinase in Motion: Insights into the Dynamic Nature of p38α by High-Pressure NMR Spectroscopic Studies. Chembiochem 2013; 14:1799-806. [DOI: 10.1002/cbic.201300170] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2013] [Indexed: 11/11/2022]
|
19
|
|
20
|
Kaas Q, Craik DJ. NMR of plant proteins. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2013; 71:1-34. [PMID: 23611313 DOI: 10.1016/j.pnmrs.2013.01.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/02/2013] [Accepted: 01/21/2013] [Indexed: 06/02/2023]
Affiliation(s)
- Quentin Kaas
- The University of Queensland, Institute for Molecular Bioscience, Brisbane, Queensland 4072, Australia
| | | |
Collapse
|
21
|
Drobizhev M, Scott JN, Callis PR, Rebane A. All-Optical Sensing of the Components of the Internal Local Electric Field in Proteins. IEEE PHOTONICS JOURNAL 2012; 4:1996-2001. [PMID: 25419440 PMCID: PMC4238891 DOI: 10.1109/jphot.2012.2221124] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Here, we present a new all-optical method of interrogation of the internal electric field vector inside proteins. The method is based on experimental evaluation of the permanent dipole moment change upon excitation and the pure electronic transition frequency of a fluorophore embedded in a protein matrix. The permanent dipole moment change can be obtained from two-photon absorption measurements. In addition, permanent dipole moment change, tensor of polarizability change, and transition frequency for the free chromophore should be calculated quantum-mechanically. This allows obtaining the components of the electric field by considering the second-order Stark shift. We use the fluorescent protein mCherry as an example to demonstrate the applicability of the method.
Collapse
Affiliation(s)
- M Drobizhev
- Department of Physics, Montana State University, Bozeman, MT 59717 USA
| | - J N Scott
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717 USA
| | - P R Callis
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT 59717 USA
| | - A Rebane
- Department of Physics, Montana State University, Bozeman, MT 59717 USA
| |
Collapse
|
22
|
Sahakyan AB. Computational studies of dielectric permittivity effects on chemical shifts of alanine dipeptide. Chem Phys Lett 2012. [DOI: 10.1016/j.cplett.2012.07.069] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
|
23
|
McIntosh LP, Naito D, Baturin SJ, Okon M, Joshi MD, Nielsen JE. Dissecting electrostatic interactions in Bacillus circulans xylanase through NMR-monitored pH titrations. JOURNAL OF BIOMOLECULAR NMR 2011; 51:5-19. [PMID: 21947911 DOI: 10.1007/s10858-011-9537-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Accepted: 06/25/2011] [Indexed: 05/31/2023]
Abstract
NMR-monitored pH titration curves of proteins provide a rich source of structural and electrostatic information. Although relatively straightforward to measure, interpreting pH-dependent chemical shift changes to obtain site-specific acid dissociation constants (pK (A) values) is challenging. In order to analyze the biphasic titrations exhibited by the side chain (13)C(γ) nuclei of the nucleophilic Glu78 and general acid/base Glu172 in Bacillus circulans xylanase, we have revisited the formalism for the ionization equilibria of two coupled acidic residues. In general, fitting NMR-monitored pH titration curves for such a system will only yield the two macroscopic pK (A) values that reflect the combined effects of both deprotonation reactions. However, through the use of mutations complemented with ionic strength-dependent measurements, we are able to extract the four microscopic pK (Ai) values governing the branched acid/base equilibria of Glu78 and Glu172 in BcX. These data, confirmed through theoretical calculations, help explain the pH-dependent mechanism of this model GH11 xylanase by demonstrating that the kinetically determined pK (A) values and hence catalytic roles of these two residues result from their electrostatic coupling.
Collapse
Affiliation(s)
- Lawrence P McIntosh
- Department of Biochemistry and Molecular Biology, Department of Chemistry, and Michael Smith Laboratories, Life Sciences Centre, University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC V6T 1Z3, Canada.
| | | | | | | | | | | |
Collapse
|
24
|
Abstract
Accurate computational methods for predicting electrostatic energies are of major importance for our understanding of protein energetics in general for computer-aided drug design as well as for the design of novel biocatalysts and protein therapeutics. Electrostatic energies are of particular importance in such applications as virtual screening, drug design and protein-protein docking due to the high charge density of protein ligands and small-molecule drugs, and the frequent protonation state changes observed when drugs bind to their protein targets. Therefore, the development of a reliable and fast algorithm for the evaluation of electrostatic free energies, as an important contributor to the overall protein energy function, has been the focus for many scientists over the past three decades. In this review we describe the current state-of-the-art in modeling electrostatic effects in proteins and protein-ligand complexes. We focus mainly on the merits and drawbacks of the continuum methodology, and speculate on future directions in refining algorithms for calculating electrostatic energies in proteins using experimental data.
Collapse
|
25
|
Webb H, Tynan-Connolly BM, Lee GM, Farrell D, O'Meara F, Søndergaard CR, Teilum K, Hewage C, McIntosh LP, Nielsen JE. Remeasuring HEWL pK(a) values by NMR spectroscopy: methods, analysis, accuracy, and implications for theoretical pK(a) calculations. Proteins 2010; 79:685-702. [PMID: 21287606 DOI: 10.1002/prot.22886] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Revised: 08/24/2010] [Accepted: 09/03/2010] [Indexed: 11/08/2022]
Abstract
Site-specific pK(a) values measured by NMR spectroscopy provide essential information on protein electrostatics, the pH-dependence of protein structure, dynamics and function, and constitute an important benchmark for protein pK(a) calculation algorithms. Titration curves can be measured by tracking the NMR chemical shifts of several reporter nuclei versus sample pH. However, careful analysis of these curves is needed to extract residue-specific pK(a) values since pH-dependent chemical shift changes can arise from many sources, including through-bond inductive effects, through-space electric field effects, and conformational changes. We have re-measured titration curves for all carboxylates and His 15 in Hen Egg White Lysozyme (HEWL) by recording the pH-dependent chemical shifts of all backbone amide nitrogens and protons, Asp/Glu side chain protons and carboxyl carbons, and imidazole protonated carbons and protons in this protein. We extracted pK(a) values from the resulting titration curves using standard fitting methods, and compared these values to each other, and with those measured previously by ¹H NMR (Bartik et al., Biophys J 1994;66:1180–1184). This analysis gives insights into the true accuracy associated with experimentally measured pK(a) values. We find that apparent pK(a) values frequently differ by 0.5–1.0 units depending upon the nuclei monitored, and that larger differences occasionally can be observed. The variation in measured pK(a) values, which reflects the difficulty in fitting and assigning pH-dependent chemical shifts to specific ionization equilibria, has significant implications for the experimental procedures used for measuring protein pK(a) values, for the benchmarking of protein pK(a) calculation algorithms, and for the understanding of protein electrostatics in general.
Collapse
Affiliation(s)
- Helen Webb
- School of Biomolecular and Biomedical Science, Centre for Synthesis and Chemical Biology, UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland
| | | | | | | | | | | | | | | | | | | |
Collapse
|
26
|
Tarasek MR, Kempf JG. Radiofrequency quadrupolar NMR stark spectroscopy: steady state response calibration and tensorial mapping. J Phys Chem A 2010; 114:10634-45. [PMID: 20839890 DOI: 10.1021/jp107920x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Radiofrequency electric (E) fields oscillating at twice the usual NMR frequency (2ω(0)) can induce double-quantum transitions in quadrupolar nuclei, an NMR Stark effect. Characterization of such is of interest to aid understanding of electrostatic effects in NMR spectra. Calibration of Stark responses to an applied electric field may also be used to assess native fields within molecules and materials. We present high-field (14.1 T), room-temperature NMR experiments to calibrate the 2ω(0) Stark response in crystalline GaAs. This system presents an important test of current techniques and conditions, as historical studies at low field (500-900 mT) and low temperature (77 K) provide a basis for comparison. Our measurements of steady state response reveal the quadrupolar Stark tuning rate for (69)Ga in this material. The value, β(Q) = (11.5 ± 0.1) × 10(12) m(-1), is 3.6 times larger than the most-reliable prior result. In the process, we also uncovered a previously unobserved double-quantum steady state coherence. It appears as a completely separable dispersive signal component in quadrature-detected presaturation spectra versus offset from 2ω(0). The new component may eventually afford an independent route to calibrating β(Q). Finally, we demonstrated exceptional agreement with theory of the orientation-dependent Stark response for rotation of the sample relative to B(0) over a range of 90° and for E-field amplitudes from 30-180 V/cm.
Collapse
Affiliation(s)
- Matthew R Tarasek
- Department of Chemistry and Chemical Biology and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
| | | |
Collapse
|
27
|
Pomin VH, Sharp JS, Li X, Wang L, Prestegard JH. Characterization of glycosaminoglycans by 15N NMR spectroscopy and in vivo isotopic labeling. Anal Chem 2010; 82:4078-88. [PMID: 20423049 DOI: 10.1021/ac1001383] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Characterization of glycosaminoglycans (GAGs), including chondroitin sulfate (CS), dermatan sulfate (DS), and heparan sulfate (HS), is important in developing an understanding of cellular function and in assuring quality of preparations destined for biomedical applications. While use of (1)H and (13)C NMR spectroscopy has become common in characterization of these materials, spectra are complex and difficult to interpret when a more heterogeneous GAG type or a mixture of several types is present. Herein a method based on (1)H-(15)N two-dimensional NMR experiments is described. The (15)N- and (1)H-chemical shifts of amide signals from (15)N-containing acetylgalactosamines in CSs are shown to be quite sensitive to the sites of sulfation (4-, 6-, or 4,6-) and easily distinguishable from those of DS. The amide signals from residual (15)N-containing acetylglucosamines in HS are shown to be diagnostic of the presence of these GAG components as well. Most data were collected at natural abundance of (15)N despite its low percentage. However enrichment of the (15)N-content in GAGs using metabolic incorporation from (15)N-glutamine added to cell culture media is also demonstrated and used to distinguish metabolic states in different cell types.
Collapse
Affiliation(s)
- Vitor H Pomin
- Complex Carbohydrate Research Center, 315 Riverbend Road, University of Georgia, Athens, Georgia 30602, USA
| | | | | | | | | |
Collapse
|
28
|
Tomlinson JH, Green VL, Baker PJ, Williamson MP. Structural origins of pH-dependent chemical shifts in the B1 domain of protein G. Proteins 2010; 78:3000-16. [DOI: 10.1002/prot.22825] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
29
|
Tremblay ML, Banks AW, Rainey JK. The predictive accuracy of secondary chemical shifts is more affected by protein secondary structure than solvent environment. JOURNAL OF BIOMOLECULAR NMR 2010; 46:257-270. [PMID: 20213252 DOI: 10.1007/s10858-010-9400-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Accepted: 02/17/2010] [Indexed: 05/28/2023]
Abstract
Biomolecular NMR spectroscopy frequently employs estimates of protein secondary structure using secondary chemical shift (Deltadelta) values, measured as the difference between experimental and random coil chemical shifts (RCCS). Most published random coil data have been determined in aqueous conditions, reasonable for non-membrane proteins, but potentially less relevant for membrane proteins. Two new RCCS sets are presented here, determined in dimethyl sulfoxide (DMSO) and chloroform:methanol:water (4:4:1 by volume) at 298 K. A web-based program, CS-CHEMeleon, has been implemented to determine the accuracy of secondary structure assessment by calculating and comparing Deltadelta values for various RCCS datasets. Using CS-CHEMeleon, Deltadelta predicted versus experimentally determined secondary structures were compared for large datasets of membrane and non-membrane proteins as a function of RCCS dataset, Deltadelta threshold, nucleus, localized parameter averaging and secondary structure type. Optimized Deltadelta thresholds are presented both for published and for the DMSO and chloroform:methanol:water derived RCCS tables. Despite obvious RCCS variations between datasets, prediction of secondary structure was consistently similar. Strikingly, predictive accuracy seems to be most dependent upon the type of secondary structure, with helices being the most accurately predicted by Deltadelta values using five different RCCS tables. We suggest caution when using Deltadelta-based restraints in structure calculations as the underlying dataset may be biased. Comparative assessment of multiple RCCS datasets should be performed, and resulting Deltadelta-based restraints weighted appropriately relative to other experimental restraints.
Collapse
Affiliation(s)
- Marie-Laurence Tremblay
- Department of Biochemistry & Molecular Biology, Dalhousie University, Halifax, NS, B3H 1X5, Canada
| | | | | |
Collapse
|
30
|
Farrell D, Miranda ES, Webb H, Georgi N, Crowley PB, McIntosh LP, Nielsen JE. Titration_DB: storage and analysis of NMR-monitored protein pH titration curves. Proteins 2010; 78:843-57. [PMID: 19899070 DOI: 10.1002/prot.22611] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
NMR-monitored pH titration experiments are routinely used to measure site-specific protein pKa values. Accurate experimental pKa values are essential in dissecting enzyme catalysis, in studying the pH-dependence of protein stability and ligand binding, in benchmarking pKa prediction algorithms, and ultimately in understanding electrostatic effects in proteins. However, due to the complex ways in which pH-dependent electrostatic and structural changes manifest themselves in NMR spectra, reported apparent pKa values are often dependent on the way that NMR pH-titration curves are analyzed. It is therefore important to retain the raw NMR spectroscopic data to allow for documentation and possible re-interpretation. We have constructed a database of primary NMR pH-titration data, which is accessible via a web interface. Here, we report statistics of the database contents and analyze the data with a global perspective to provide guidelines on best practice for fitting NMR titration curves. Titration_DB is available at http://enzyme.ucd.ie/Titration_DB. Proteins 2010. (c) 2009 Wiley-Liss, Inc.
Collapse
Affiliation(s)
- Damien Farrell
- School of Biomolecular and Biomedical Science, Centre for Synthesis and Chemical Biology, UCD Conway Institute, University College Dublin, Belfield, Dublin 4, Ireland
| | | | | | | | | | | | | |
Collapse
|
31
|
Rougier L, Milon A, Réat V, Jolibois F. Modelling the influence of hydrogen bond network on chemical shielding tensors description. GIAO-DFT study of WALP23 transmembrane α-helix as a test case. Phys Chem Chem Phys 2010; 12:6999-7008. [DOI: 10.1039/b923883b] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
32
|
Kukić P, Farrell D, Søndergaard CR, Bjarnadottir U, Bradley J, Pollastri G, Nielsen JE. Improving the analysis of NMR spectra tracking pH-induced conformational changes: Removing artefacts of the electric field on the NMR chemical shift. Proteins 2009; 78:971-84. [DOI: 10.1002/prot.22621] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
33
|
Hass MAS, Yilmaz A, Christensen HEM, Led JJ. Histidine side-chain dynamics and protonation monitored by 13C CPMG NMR relaxation dispersion. JOURNAL OF BIOMOLECULAR NMR 2009; 44:225-233. [PMID: 19533375 DOI: 10.1007/s10858-009-9332-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2009] [Accepted: 05/28/2009] [Indexed: 05/27/2023]
Abstract
The use of 13C NMR relaxation dispersion experiments to monitor micro-millisecond fluctuations in the protonation states of histidine residues in proteins is investigated. To illustrate the approach, measurements on three specifically 13C labeled histidine residues in plastocyanin (PCu) from Anabaena variabilis (A.v.) are presented. Significant Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion is observed for 13C(epsilon1) nuclei in the histidine imidazole rings of A.v. PCu. The chemical shift changes obtained from the CPMG dispersion data are in good agreement with those obtained from the chemical shift titration experiments, and the CPMG derived exchange rates agree with those obtained previously from 15N backbone relaxation measurements. Compared to measurements of backbone nuclei, 13C(epsilon1) dispersion provides a more direct method to monitor interchanging protonation states or other kinds of conformational changes of histidine side chains or their environment. Advantages and shortcomings of using the 13C(epsilon1) dispersion experiments in combination with chemical shift titration experiments to obtain information on exchange dynamics of the histidine side chains are discussed.
Collapse
Affiliation(s)
- Mathias A S Hass
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen Ø, Denmark
| | | | | | | |
Collapse
|
34
|
Hass MAS, Vlasie MD, Ubbink M, Led JJ. Conformational exchange in pseudoazurin: different kinds of microsecond to millisecond dynamics characterized by their pH and buffer dependence using 15N NMR relaxation. Biochemistry 2009; 48:50-8. [PMID: 19072172 DOI: 10.1021/bi801858f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The dynamics of the reduced form of the blue copper protein pseudoazurin from Alcaligenes faecalis S-6 was investigated using (15)N relaxation measurements with a focus on the dynamics of the micro- to millisecond time scale. Different types of conformational exchange processes are observed in the protein on this time scale. At low pH, the protonation of the C-terminal copper-ligated histidine, His81, is observed. A comparison of the exchange rates in the presence and absence of added buffers shows that the protonation is the rate-limiting step at low buffer concentrations. This finding agrees with previous observations for other blue copper proteins, e.g., amicyanin and plastocyanin. However, in contrast to plastocyanin but similar to amicyanin, a second conformational exchange between different conformations of the protonated copper site is observed at low pH, most likely triggered by the protonation of His81. This process has been further characterized using CPMG dispersion methods and is found to occur with a rate of a few thousands per second. Finally, micro- to millisecond motions are observed in one of the loop regions and in the alpha-helical regions. These motions are unaffected by pH and are unrelated to the conformational changes in the active site of pseudoazurin.
Collapse
Affiliation(s)
- Mathias A S Hass
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark
| | | | | | | |
Collapse
|
35
|
Hass MAS, Hansen DF, Christensen HEM, Led JJ, Kay LE. Characterization of Conformational Exchange of a Histidine Side Chain: Protonation, Rotamerization, and Tautomerization of His61 in Plastocyanin from Anabaena variabilis. J Am Chem Soc 2008; 130:8460-70. [DOI: 10.1021/ja801330h] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mathias A. S. Hass
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark, Departments of Molecular Genetics, Biochemistry, and Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8, and Department of Chemistry, The Technical University of Denmark, 2800 Lyngby, Denmark
| | - D. Flemming Hansen
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark, Departments of Molecular Genetics, Biochemistry, and Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8, and Department of Chemistry, The Technical University of Denmark, 2800 Lyngby, Denmark
| | - Hans E. M. Christensen
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark, Departments of Molecular Genetics, Biochemistry, and Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8, and Department of Chemistry, The Technical University of Denmark, 2800 Lyngby, Denmark
| | - Jens J. Led
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark, Departments of Molecular Genetics, Biochemistry, and Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8, and Department of Chemistry, The Technical University of Denmark, 2800 Lyngby, Denmark
| | - Lewis E. Kay
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen Ø, Denmark, Departments of Molecular Genetics, Biochemistry, and Chemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8, and Department of Chemistry, The Technical University of Denmark, 2800 Lyngby, Denmark
| |
Collapse
|
36
|
Analyzing Protein NMR pH-Titration Curves. ACTA ACUST UNITED AC 2008. [DOI: 10.1016/s1574-1400(08)00005-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|