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Rozhkov SP, Goryunov AS. Possible Phase Effects in the Dispersion of a Globular Protein in the Temperature Range of the Native State. Biophysics (Nagoya-shi) 2022. [DOI: 10.1134/s0006350922060215] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023] Open
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2
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Zhang ZC, Hales DA, Clemmer DE. Influence of N Terminus Amino Acid on Peptide Cleavage in Solution through Diketopiperazine Formation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:1368-1376. [PMID: 35576623 PMCID: PMC10161955 DOI: 10.1021/jasms.2c00037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Diketopiperazine (DKP) formation is an important degradation pathway for peptides and proteins. It can occur during synthesis and storage in either solution or the solid state. The kinetics of peptide cleavage through DKP formation have been analyzed for the model peptides Xaa1-Pro2-Gly4-Lys7 [Xaa = Gln, Glu, Lys, Ser, Phe, Trp, Tyr, Cha (β-cyclohexylalanine), Aib (α-aminoisobutyric acid), Gly, and Val] at multiple elevated temperatures in ethanol with ion mobility spectrometry-mass spectrometry (IMS-MS). When Xaa is an amino acid with a charged or polar side chain, degradation is relatively fast. When Xaa is an amino acid with a nonpolar alkyl side chain, the peptide is relatively stable. For these peptides, a bulky group on the α carbon speeds up dissociation, but the kinetic effects vary in a complicated manner for bulky groups on the β or γ carbon. Peptides where Xaa has a nonpolar aromatic side chain show moderate dissociation rates. The stability of these peptides is a result of multiple factors. The reaction rate is enhanced by (1) the stabilization of the late transition state through the interaction of an aromatic ring with the nascent DKP ring or lowering the activation energy of nucleophilic attack intermediate state through polar or charged residues and (2) the preference of the cis proline bond favored by the aromatic N-terminus. The number of unseen intermediates and transition state thermodynamic values are derived for each peptide by modeling the kinetics data. Most of the transition states are entropically favored (ΔS⧧ ∼ -5 to +31 J·mol-1·K-1), and all are enthalpically disfavored (ΔH⧧ ∼ 93 to 109 kJ·mol-1). The Gibbs free energy of activation is similar for all of the peptides studied here (ΔG⧧ ∼ 90-99 kJ·mol-1).
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Affiliation(s)
- Zhi-Chao Zhang
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - David A Hales
- Department of Chemistry, Hendrix College, Conway, Arkansas 72032, United States
| | - David E Clemmer
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
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3
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Laganowsky A, Clemmer DE, Russell DH. Variable-Temperature Native Mass Spectrometry for Studies of Protein Folding, Stabilities, Assembly, and Molecular Interactions. Annu Rev Biophys 2021; 51:63-77. [PMID: 34932911 PMCID: PMC9086101 DOI: 10.1146/annurev-biophys-102221-101121] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The structures and conformational dynamics of proteins, protein complexes, and their noncovalent interactions with other molecules are controlled specifically by the Gibbs free energy (entropy and enthalpy) of the system. For some organisms, temperature is highly regulated, but the majority of biophysical studies are carried out at room, nonphysiological temperature. In this review, we describe variable-temperature electrospray ionization (vT-ESI) mass spectrometry (MS)-based studies with unparalleled sensitivity, dynamic range, and selectivity for studies of both cold- and heat-induced chemical processes. Such studies provide direct determinations of stabilities, reactivities, and thermodynamic measurements for native and non-native structures of proteins and protein complexes and for protein-ligand interactions. Highlighted in this review are vT-ESI-MS studies that reveal 40 different conformers of chymotrypsin inhibitor 2, a classic two-state (native → unfolded) unfolder, and thermochemistry for a model membrane protein system binding lipid and its regulatory protein. Expected final online publication date for the Annual Review of Biophysics, Volume 51 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Arthur Laganowsky
- Department of Chemistry, Texas A&M University, College Station, Texas, USA; ,
| | - David E Clemmer
- Department of Chemistry, Indiana University, Bloomington, Indiana, USA;
| | - David H Russell
- Department of Chemistry, Texas A&M University, College Station, Texas, USA; ,
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4
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Zhang Z, Conant CR, El-Baba TJ, Raab SA, Fuller DR, Hales DA, Clemmer DE. Diketopiperazine Formation from FPG nK ( n = 1-9) Peptides: Rates of Structural Rearrangements and Mechanisms. J Phys Chem B 2021; 125:8107-8116. [PMID: 34270248 PMCID: PMC10661757 DOI: 10.1021/acs.jpcb.1c03515] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Peptides with penultimate proline residues undergo trans → cis isomerization of the Phe1-Pro2 peptide bond followed by spontaneous bond cleavage at the Pro2-Xxx3 bond (where Xxx is another amino acid residue), leading to cleavage of the Pro2-Xxx3 bond and formation of a diketopiperazine (DKP). In this paper, ion mobility spectrometry and mass spectrometry techniques were used to study the dissociation kinetics of nine peptides [Phe1-Pro2-Glyn-Lysn+3 (n = 1-9)] in ethanol. Shorter (n = 1-3) peptides are found to be more stable than longer (n = 4-9) peptides. Alanine substitution studies indicate that, when experiments are initiated, the Phe1-Pro2 bond of the n = 9 peptide exists exclusively in the cis configuration, while the n = 1-8 peptides appear to exist initially with both cis- and trans-Phe1-Pro2 configured bonds. Molecular dynamics simulations indicate that intramolecular hydrogen bonding interactions stabilize conformations of shorter peptides, thus inhibiting DKP formation. Similar stabilizing interactions appear less frequently in longer peptides. In addition, in smaller peptides, the N-terminal amino group is more likely to be charged compared to the same group in longer peptides, which would inhibit the dissociation through the DKP formation mechanism. Analysis of temperature-dependent kinetics measurements provides insight about the mechanism of bond cleavage. The analysis gives the following transition state thermochemistry: ΔG⧧ values range from 94.6 ± 0.9 to 101.5 ± 1.9 kJ·mol-1, values of ΔH⧧ range from 89.1 ± 0.9 to 116.7 ± 1.5 kJ·mol-1, and ΔS⧧ values range from -25.4 ± 2.6 to 50.8 ± 4.2 J·mol-1·K-1. Proposed mechanisms and thermochemistry are discussed.
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Affiliation(s)
- Zhichao Zhang
- Department of Chemistry, Indiana University, Bloomington, Indiana, United States
| | - Christopher R Conant
- Department of Chemistry, Indiana University, Bloomington, Indiana, United States
| | - Tarick J El-Baba
- Department of Chemistry, Indiana University, Bloomington, Indiana, United States
| | - Shannon A Raab
- Department of Chemistry, Indiana University, Bloomington, Indiana, United States
| | - Daniel R Fuller
- Department of Chemistry, Indiana University, Bloomington, Indiana, United States
| | - David A Hales
- Department of Chemistry, Hendrix College, Conway, Arkansas, United States
| | - David E Clemmer
- Department of Chemistry, Indiana University, Bloomington, Indiana, United States
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5
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McCabe JW, Shirzadeh M, Walker TE, Lin CW, Jones BJ, Wysocki VH, Barondeau DP, Clemmer DE, Laganowsky A, Russell DH. Variable-Temperature Electrospray Ionization for Temperature-Dependent Folding/Refolding Reactions of Proteins and Ligand Binding. Anal Chem 2021; 93:6924-6931. [PMID: 33904705 DOI: 10.1021/acs.analchem.1c00870] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Stabilities and structure(s) of proteins are directly coupled to their local environment or Gibbs free energy landscape as defined by solvent, temperature, pressure, and concentration. Solution pH, ionic strength, cofactors, chemical chaperones, and osmolytes perturb the chemical potential and induce further changes in structure, stability, and function. At present, no single analytical technique can monitor these effects in a single measurement. Mass spectrometry and ion mobility-mass spectrometry play increasingly essential roles in studies of proteins, protein complexes, and even membrane protein complexes; however, with few exceptions, the effects of the solution temperature on the stability and structure(s) of analytes have not been thoroughly investigated. Here, we describe a new variable-temperature electrospray ionization (vT-ESI) source that utilizes a thermoelectric chip to cool and heat the solution contained within the static ESI emitter. This design allows for solution temperatures to be varied from ∼5 to 98 °C with short equilibration times (<2 min) between precisely controlled temperature changes. The performance of the apparatus for vT-ESI-mass spectrometry and vT-ESI-ion mobility-mass spectrometry studies of cold- and heat-folding reactions is demonstrated using ubiquitin and frataxin. Instrument performance for studies on temperature-dependent ligand binding is shown using the chaperonin GroEL.
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Affiliation(s)
- Jacob W McCabe
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Mehdi Shirzadeh
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Thomas E Walker
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Cheng-Wei Lin
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Benjamin J Jones
- Department of Chemistry, Ohio State University, Columbus, Ohio 43210, United States
| | - Vicki H Wysocki
- Department of Chemistry, Ohio State University, Columbus, Ohio 43210, United States
| | - David P Barondeau
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - David E Clemmer
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Arthur Laganowsky
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - David H Russell
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
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6
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McCabe JW, Hebert MJ, Shirzadeh M, Mallis CS, Denton JK, Walker TE, Russell DH. THE IMS PARADOX: A PERSPECTIVE ON STRUCTURAL ION MOBILITY-MASS SPECTROMETRY. MASS SPECTROMETRY REVIEWS 2021; 40:280-305. [PMID: 32608033 PMCID: PMC7989064 DOI: 10.1002/mas.21642] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Accepted: 06/03/2020] [Indexed: 05/06/2023]
Abstract
Studies of large proteins, protein complexes, and membrane protein complexes pose new challenges, most notably the need for increased ion mobility (IM) and mass spectrometry (MS) resolution. This review covers evolutionary developments in IM-MS in the authors' and key collaborators' laboratories with specific focus on developments that enhance the utility of IM-MS for structural analysis. IM-MS measurements are performed on gas phase ions, thus "structural IM-MS" appears paradoxical-do gas phase ions retain their solution phase structure? There is growing evidence to support the notion that solution phase structure(s) can be retained by the gas phase ions. It should not go unnoticed that we use "structures" in this statement because an important feature of IM-MS is the ability to deal with conformationally heterogeneous systems, thus providing a direct measure of conformational entropy. The extension of this work to large proteins and protein complexes has motivated our development of Fourier-transform IM-MS instruments, a strategy first described by Hill and coworkers in 1985 (Anal Chem, 1985, 57, pp. 402-406) that has proved to be a game-changer in our quest to merge drift tube (DT) and ion mobility and the high mass resolution orbitrap MS instruments. DT-IMS is the only method that allows first-principles determinations of rotationally averaged collision cross sections (CSS), which is essential for studies of biomolecules where the conformational diversities of the molecule precludes the use of CCS calibration approaches. The Fourier transform-IM-orbitrap instrument described here also incorporates the full suite of native MS/IM-MS capabilities that are currently employed in the most advanced native MS/IM-MS instruments. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.
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Affiliation(s)
- Jacob W McCabe
- Department of Chemistry, Texas A&M University, College Station, TX, 77843
| | - Michael J Hebert
- Department of Chemistry, Texas A&M University, College Station, TX, 77843
| | - Mehdi Shirzadeh
- Department of Chemistry, Texas A&M University, College Station, TX, 77843
| | | | - Joanna K Denton
- Department of Chemistry, Texas A&M University, College Station, TX, 77843
| | - Thomas E Walker
- Department of Chemistry, Texas A&M University, College Station, TX, 77843
| | - David H Russell
- Department of Chemistry, Texas A&M University, College Station, TX, 77843
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7
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Zhang ZC, Raab SA, Hales DA, Clemmer DE. Influence of Solvents upon Diketopiperazine Formation of FPG8K. J Phys Chem B 2021; 125:2952-2959. [DOI: 10.1021/acs.jpcb.1c00269] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Zhi-chao Zhang
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, Indiana 47401, United States
| | - Shannon A. Raab
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, Indiana 47401, United States
| | - David A. Hales
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, Indiana 47401, United States
- Department of Chemistry, Hendrix College, Conway, Arkansas 72032, United States
| | - David E. Clemmer
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, Indiana 47401, United States
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8
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Pal S, Banerjee S, Prabhakaran EN. Helix-Coil Transition at a Glycine Following a Nascent α-Helix: A Synergetic Guidance Mechanism for Helix Growth. J Phys Chem A 2020; 124:7478-7490. [PMID: 32877193 DOI: 10.1021/acs.jpca.0c05489] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
A detailed understanding of forces guiding the rapid folding of a polypeptide from an apparently random coil state to an ordered α-helical structure following the rate-limiting preorganization of the initial three residue backbones into helical conformation is imperative to comprehending and regulating protein folding and for the rational design of biological mimetics. However, several details of this process are still unknown. First, although the helix-coil transition was proposed to originate at the residue level (J. Chem. Phys. 1959, 31, 526-535; J. Chem. Phys. 1961, 34, 1963-1974), all helix-folding studies have only established it between time-averaged bulk states of a long-lived helix and several transiently populated random coils, along the whole helix model sequence. Second, the predominant thermodynamic forces driving either this two-state transition or the faster helix growth following helix nucleation are still unclear. Third, the conformational space of the random coil state is not well-defined unlike its corresponding α-helix. Here we investigate the restrictions placed on the conformational space of a Gly residue backbone, as a result of it immediately succeeding a nascent α-helical turn. Analyses of the temperature-dependent 1D-, 2D-NMR, FT-IR, and CD spectra and GROMACS MD simulation trajectory of a Gly residue backbone following a model α-helical turn, which is artificially rigidified by a covalent hydrogen bond surrogate, reveal that: (i) the α-helical turn guides the ϕ torsion of the Gly exclusively into either a predominantly populated entropically favored α-helical (α-ϕ) state or a scarcely populated random coil (RC-ϕ) state; (ii) the α-ϕ state of Gly in turn favors the stability of the preceding α-helical turn, while the RC-ϕ state disrupts it, revealing an entropy-driven synergetic guidance for helix growth in the residue following helix nucleation. The applicability of a current synergetic guidance mechanism to explain rapid helix growth in folded and unfolded states of proteins and helical peptides is discussed.
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Affiliation(s)
- Sunit Pal
- Department of Chemistry, Indian Institute of Science, Bangalore, Karnataka-560012, India
| | - Shreya Banerjee
- Department of Chemistry, Indian Institute of Science, Bangalore, Karnataka-560012, India
| | - Erode N Prabhakaran
- Department of Chemistry, Indian Institute of Science, Bangalore, Karnataka-560012, India
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9
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Real-Hohn A, Groznica M, Löffler N, Blaas D, Kowalski H. nanoDSF: In vitro Label-Free Method to Monitor Picornavirus Uncoating and Test Compounds Affecting Particle Stability. Front Microbiol 2020; 11:1442. [PMID: 32676065 PMCID: PMC7333345 DOI: 10.3389/fmicb.2020.01442] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 06/04/2020] [Indexed: 12/30/2022] Open
Abstract
Thermal shift assays measure the stability of macromolecules and macromolecular assemblies as a function of temperature. The Particle Stability Thermal Release Assay (PaSTRy) of picornaviruses is based on probes becoming strongly fluorescent upon binding to hydrophobic patches of the protein capsid (e.g., SYPRO Orange) or to the viral RNA genome (e.g., SYTO-82) that become exposed upon heating virus particles. PaSTRy has been exploited for studying the stability of viral mutants, viral uncoating, and the effect of capsid-stabilizing compounds. While the results were usually robust, the thermal shift assay with SYPRO Orange is sensitive to surfactants and EDTA and failed at least to correctly report the effect of excipients on an inactivated poliovirus 3 vaccine. Furthermore, interactions between the probe and capsid-binding antivirals as well as mutual competition for binding sites cannot be excluded. To overcome these caveats, we assessed differential scanning fluorimetry with a nanoDSF device as a label-free alternative. NanoDSF monitors the changes in the intrinsic tryptophan fluorescence (ITF) resulting from alterations of the 3D-structure of proteins as a function of the temperature. Using rhinovirus A2 as a model, we demonstrate that nanoDFS is well suited for recording the temperature-dependence of conformational changes associated with viral uncoating with minute amounts of sample. We compare it with orthogonal methods and correlate the increase in viral RNA exposure with PaSTRy measurements. Importantly, nanoDSF correctly identified the thermal stabilization of RV-A2 by pleconaril, a prototypic pocket-binding antiviral compound. NanoDFS is thus a label-free, high throughput-customizable, attractive alternative for the discovery of capsid-binding compounds impacting on viral stability.
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Affiliation(s)
- Antonio Real-Hohn
- Center for Medical Biochemistry, Max Perutz Labs, Vienna Biocenter, Medical University of Vienna, Vienna, Austria
| | - Martin Groznica
- Center for Medical Biochemistry, Max Perutz Labs, Vienna Biocenter, Medical University of Vienna, Vienna, Austria
| | - Nadine Löffler
- Center for Medical Biochemistry, Max Perutz Labs, Vienna Biocenter, Medical University of Vienna, Vienna, Austria
| | - Dieter Blaas
- Center for Medical Biochemistry, Max Perutz Labs, Vienna Biocenter, Medical University of Vienna, Vienna, Austria
| | - Heinrich Kowalski
- Center for Medical Biochemistry, Max Perutz Labs, Vienna Biocenter, Medical University of Vienna, Vienna, Austria
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10
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Conant CR, Fuller DR, El-Baba TJ, Zhang Z, Russell DH, Clemmer DE. Substance P in Solution: Trans-to-Cis Configurational Changes of Penultimate Prolines Initiate Non-enzymatic Peptide Bond Cleavages. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:919-931. [PMID: 30980380 PMCID: PMC6824264 DOI: 10.1007/s13361-019-02159-w] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 02/15/2019] [Accepted: 02/15/2019] [Indexed: 05/02/2023]
Abstract
We report ion mobility spectrometry and mass spectrometry studies of the non-enzymatic step-by-step degradation of substance P (subP), an 11-residue neuropeptide, with the sequence Arg1-Pro2-Lys3-Pro4-Gln5-Gln6-Phe7-Phe8-Gly9-Leu10-Met11-NH2, in ethanol. At elevated solution temperatures (55 to 75 °C), several reactions are observed, including a protonation event, i.e., [subP+2H]2+ + H+ → [subP+3H]3+, that appears to be regulated by a configurational change and two sequential bond cleavages (the Pro2-Lys3 peptide bond is cleaved to form the smaller nonapeptide Lys3-Met11-NH2 [subP(3-11)], and subsequently, subP(3-11) is cleaved at the Pro4-Gln5 peptide bond to yield the heptapeptide Gln5-Met11-NH2 [subP(5-11)]). Each of the product peptides [subP(3-11) and subP(5-11)] is accompanied by a complementary diketopiperazine (DKP): cyclo-Arg1-Pro2 (cRP) for the first cleavage, and cyclo-Lys3-Pro4 (cKP) for the second. Insight about the mechanism of degradation is obtained by comparing kinetics calculations of trial model mechanisms with experimental data. The best model of our experimental data indicates that the initial cleavage of subP is regulated by a conformational change, likely a trans→cis isomerization of the Arg1-Pro2 peptide bond. The subP(3-11) product has a long lifetime (t1/2 ~ 30 h at 55 °C) and appears to transition through several structural intermediates prior to dissociation, suggesting that subP(3-11) is initially formed with a Lys3-trans-Pro4 peptide bond configuration and that slow trans→cis isomerization regulates the second bond cleavage event as well. From these data and our model mechanisms, we obtain transition state thermochemistry ranging from ΔH‡ = 41 to 85 kJ mol-1 and ΔS‡ = - 43 to - 157 J mol-1 K-1 for each step in the reaction. Graphical Abstract.
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Affiliation(s)
- Christopher R Conant
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, IN, 47401, USA
| | - Daniel R Fuller
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, IN, 47401, USA
| | - Tarick J El-Baba
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, IN, 47401, USA
| | - Zhichao Zhang
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, IN, 47401, USA
| | - David H Russell
- Department of Chemistry, Texas A&M University, College Station, TX, 77843, USA
| | - David E Clemmer
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, IN, 47401, USA.
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11
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Hebert MJ, Russell DH. Hydration of Guanidinium Ions: An Experimental Search for Like-Charged Ion Pairs. J Phys Chem Lett 2019; 10:1349-1354. [PMID: 30840463 DOI: 10.1021/acs.jpclett.9b00268] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Guanidinium ions (GdmH+) are reported to form stable complexes (GdmH+/GdmH+) in aqueous solution despite strong repulsive interactions between the like-charged centers. These complexes are thought to play important roles in protein folding, membrane penetration, and formation of protein dimers. Although GdmH+ ions are weakly hydrated, semiempirical calculations provide evidence that these like-charged complexes are stabilized by water molecules, which serve important structural and energetic roles. Specifically, water molecules bridge between the GdmH+ ions of GdmH+/GdmH+ complexes as well as complexes involving the guanidinium side chains of arginine. Potential biological significances of like-charged complexes have been largely confirmed by ab initio molecular dynamics simulations and indirect experimental evidence. We report cryo-ion mobility-mass spectrometry results for the GdmH+/GdmH+ ion pair confined in a nanodroplet- the first direct experimental observation of this like-charged complex. A second like-charged complex, described as a water-mediated complex involving GdmH+ and H3O+, was also observed.
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Affiliation(s)
- Michael J Hebert
- Department of Chemistry Texas A&M University College Station , Texas 77843 , United States
| | - David H Russell
- Department of Chemistry Texas A&M University College Station , Texas 77843 , United States
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12
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Fuller DR, Conant CR, El-Baba TJ, Zhang Z, Molloy KR, Zhang CS, Hales DA, Clemmer DE. Monitoring the stabilities of a mixture of peptides by mass-spectrometry-based techniques. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2019; 25:73-81. [PMID: 30773926 PMCID: PMC7702224 DOI: 10.1177/1469066718798718] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Biomolecular degradation plays a key role in proteostasis. Typically, proteolytic enzymes degrade proteins into smaller peptides by breaking amino acid bonds between specific residues. Cleavage around proline residues is often missed and requires highly specific enzymes for peptide processing due to the cyclic proline side-chain. However, degradation can occur spontaneously (i.e. in the absence of enzymes). In this study, the influence of the first residue on the stability of a series of penultimate proline containing peptides, with the sequence Xaa-Pro-Gly-Gly (where Xaa is any amino acid), is investigated with mass spectrometry techniques. Peptides were incubated as mixtures at various solution temperatures (70℃ to 90℃) and were periodically sampled over the duration of the experiment. At elevated temperatures, we observe dissociation after the Xaa-Pro motif for all sequences, but at different rates. Transition state thermochemistry was obtained by studying the temperature-dependent kinetics and although all peptides show relatively small differences in the transition state free energies (∼95 kJ/mol), there is significant variability in the transition state entropy and enthalpy. This demonstrates that the side-chain of the first amino acid has a significant influence on the stability of the Xaa-Pro sequence. From these data, we demonstrate the ability to simultaneously measure the dissociation kinetics and relative transition state thermochemistries for a mixture of peptides, which vary only in the identity of the N-terminal amino acid.
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Affiliation(s)
- Daniel R Fuller
- Department of Chemistry, Indiana University, Bloomington, IN, USA
| | | | - Tarick J El-Baba
- Department of Chemistry, Indiana University, Bloomington, IN, USA
| | - Zhichao Zhang
- Department of Chemistry, Indiana University, Bloomington, IN, USA
| | | | - Connie S Zhang
- Department of Chemistry, Hendrix College, Conway, AR, USA
| | - David A Hales
- Department of Chemistry, Hendrix College, Conway, AR, USA
| | - David E Clemmer
- Department of Chemistry, Indiana University, Bloomington, IN, USA
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13
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Huang KY, Horng JC. Impacts of the Terminal Charged Residues on Polyproline Conformation. J Phys Chem B 2018; 123:138-147. [DOI: 10.1021/acs.jpcb.8b10864] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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14
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Consta S, In Oh M, Kwan V, Malevanets A. Strengths and Weaknesses of Molecular Simulations of Electrosprayed Droplets. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:2287-2296. [PMID: 30259408 DOI: 10.1007/s13361-018-2039-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2018] [Revised: 07/05/2018] [Accepted: 07/13/2018] [Indexed: 06/08/2023]
Abstract
The origin and the magnitude of the charge in a macroion are critical questions in mass spectrometry analysis coupled to electrospray and other ionization techniques that transfer analytes from the bulk solution into the gaseous phase via droplets. In many circumstances, it is the later stages of the existence of a macroion in the containing solvent drop before the detection that determines the final charge state. Experimental characterization of small (with linear dimensions of several nanometers) and short-lived droplets is quite challenging. Molecular simulations in principle may provide insight exactly in this challenging for experiments regime. We discuss the strengths and weaknesses of the molecular modeling of electrosprayed droplets using molecular dynamics. We illustrate the limitations of the molecular modeling in the analysis of large macroions and specifically proteins away from their native states. Graphical Abstract ᅟ.
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Affiliation(s)
- Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario, N6A 5B7, Canada.
| | - Myong In Oh
- Department of Chemistry, The University of Western Ontario, London, Ontario, N6A 5B7, Canada
| | - Victor Kwan
- Department of Chemistry, The University of Western Ontario, London, Ontario, N6A 5B7, Canada
| | - Anatoly Malevanets
- Department of Chemistry, The University of Western Ontario, London, Ontario, N6A 5B7, Canada
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15
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Fuller DR, Conant CR, El-Baba TJ, Brown CJ, Woodall DW, Russell DH, Clemmer DE. Conformationally Regulated Peptide Bond Cleavage in Bradykinin. J Am Chem Soc 2018; 140:9357-9360. [PMID: 30028131 PMCID: PMC6503673 DOI: 10.1021/jacs.8b04751] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ion mobility and mass spectrometry techniques are used to investigate the stabilities of different conformations of bradykinin (BK, Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9). At elevated solution temperatures, we observe a slow protonation reaction, i.e., [BK+2H]2++H+ → [BK+3H]3+, that is regulated by trans → cis isomerization of Arg1-Pro2, resulting in the Arg1- cis-Pro2- cis-Pro3-Gly4-Phe5-Ser6- cis-Pro7-Phe8-Arg9 (all- cis) configuration. Once formed, the all- cis [BK+3H]3+ spontaneously cleaves the bond between Pro2-Pro3 with perfect specificity, a bond that is biologically resistant to cleavage by any human enzyme. Temperature-dependent kinetics studies reveal details about the intrinsic peptide processing mechanism. We propose that nonenzymatic cleavage at Pro2-Pro3 occurs through multiple intermediates and is regulated by trans → cis isomerization of Arg1-Pro2. From this mechanism, we can extract transition state thermochemistry: Δ G‡ = 94.8 ± 0.2 kJ·mol-1, Δ H‡ = 79.8 ± 0.2 kJ·mol-1, and Δ S‡ = -50.4 ± 1.7 J·mol-1·K-1 for the trans → cis protonation event; and, Δ G‡ = 94.1 ± 9.2 kJ·mol-1, Δ H‡ = 107.3 ± 9.2 kJ·mol-1, and Δ S‡ = 44.4 ± 5.1 J·mol-1·K-1 for bond cleavage. Biological resistance to the most favored intrinsic processing pathway prevents formation of Pro3-Gly4-Phe5-Ser6- cis-Pro7-Phe8-Arg9 that is approximately an order of magnitude more antigenic than BK.
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Affiliation(s)
- Daniel R. Fuller
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Christopher R. Conant
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Tarick J. El-Baba
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Christopher J. Brown
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Daniel W. Woodall
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - David H. Russell
- Department of Chemistry, Texas A&M University, College Station, Texas 77842, United States
| | - David E. Clemmer
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
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16
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Singh V, Biswas P. Estimating the mean first passage time of protein misfolding. Phys Chem Chem Phys 2018; 20:5692-5698. [PMID: 29410980 DOI: 10.1039/c7cp06918a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Most theoretical and experimental studies confirm that proteins fold in the time scale of microseconds to milliseconds, but the kinetics of the protein misfolding remains largely unexplored. The kinetics of unfolding-folding-misfolding equilibrium in proteins is formulated in the analytical framework of the Master equation. The folded, unfolded and the misfolded state are characterized in terms of their respective contacts. The Mean First Passage Time (MFPT) to acquire the misfolded conformation from the native or folded state is derived from this equation with different boundary conditions. The MFPT is found to be practically independent of the length of the protein, the number of native contacts and the rate constant for the misfolded to the folded state. The results obtained from the survival probability are directly correlated to the age of onset and appearance of misfolding diseases in humans.
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Affiliation(s)
- Vishal Singh
- Department of Chemistry, University of Delhi, Delhi-110007, India.
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