1
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Webb IK. Revealing the Fates of Proteins in the Gas Phase. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2024; 504:117312. [PMID: 39184132 PMCID: PMC11340257 DOI: 10.1016/j.ijms.2024.117312] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/27/2024]
Abstract
The ability to observe intact proteins by native mass spectrometry allows measurements of size, oligomeric state, numbers and types of ligands and post translational modifications bound, among many other characteristics. These studies have the potential to, and in some cases are, advancing our understanding of the role of structure in protein biology and biochemistry. However, there are some long-unresolved questions about to what extent solution-like structures persist without solvent in the vacuum of the mass spectrometer. Strong evidence from multiple sources over the years has demonstrated that well-folded proteins maintain native-like states if care is taken during sample preparation, ionization, and transmission through the gas phase. For partially unfolded states, dynamic and disordered proteins, and other important landmarks along the protein folding/unfolding pathway, caution has been urged in the interpretation of the results of native ion mobility/mass spectrometric data. New gas-phase tools allow us to provide insight into these questions with in situ, in vacuo labeling reactions delivered through ion/ion chemistry. This Young Scientist Perspective demonstrates the robustness of these tools in describing native-like structure as well as possible deviations from native-like structure during native ion mobility/mass spectrometry. This Perspective illustrates some of the changes in structure produced by the removal of solvent and details some of the challenges and potential of the field.
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Affiliation(s)
- Ian K Webb
- Department of Chemistry and Chemical Biology, Indiana University Indianapolis, Indianapolis, IN 46202
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2
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Jeanne Dit Fouque K, Molano-Arevalo JC, Leng F, Fernandez-Lima F. Conformational and Structural Characterization of Knotted Proteins. Biochemistry 2024; 63:2293-2299. [PMID: 39189377 DOI: 10.1021/acs.biochem.4c00218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/28/2024]
Abstract
Knotted proteins are fascinating natural biomolecules whose backbones entangle themselves in a knot. Their particular knotted configurations provide them with a wide range of topological features. However, their folding/unfolding mechanisms, stability, and function are poorly understood. In the present work, native trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) was used for characterizing structural features of two model knotted proteins: a Gordian 52 knot ubiquitin C-terminal hydrolase (UCH) and a Stevedore 61 knot (α-haloacid dehalogenase, DehI). Experimental results showed structural transitions of UCH and DehI as a function of solution composition (0-50% MeOH) and temperature (T ∼20-95 °C). An increase in the protein charge states and collision cross sections (∼2750-8750 Å2 and ∼3250-15,385 Å2 for UCH and DehI, respectively) with the solution organic content (OC) and temperature suggested a three-step unfolding pathway with at least four structural transitions. Results also showed that the integrity of the UCH knot core was more resistant to thermal unfolding when compared to DehI; however, both knot cores can be disrupted with the increase in the solution OC. Additional enzymatic digestion experiments using carboxypeptidase Y combined with molecular dynamics simulations showed that the knot core was preserved between Glu20 and Glu188 and Arg89 and His304 residues for UCH and DehI, respectively, where disruption of the knot core led to structural collapse followed by unfolding events. This work highlights the potential of solution OC and temperature studies combined with native TIMS-MS for the comprehensive characterization of knotted proteins to gain a better understanding of their structural transitions.
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Affiliation(s)
- Kevin Jeanne Dit Fouque
- Department of Chemistry and Biochemistry and Biomolecular Sciences Institute, Florida International University, Miami, Florida, 33199, United States
| | - Juan Camilo Molano-Arevalo
- Department of Chemistry and Biochemistry and Biomolecular Sciences Institute, Florida International University, Miami, Florida, 33199, United States
| | - Fenfei Leng
- Department of Chemistry and Biochemistry and Biomolecular Sciences Institute, Florida International University, Miami, Florida, 33199, United States
| | - Francisco Fernandez-Lima
- Department of Chemistry and Biochemistry and Biomolecular Sciences Institute, Florida International University, Miami, Florida, 33199, United States
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3
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Yoo IT, Jeong J, Eun HJ, Yun J, Heo J, Kim NJ. Conformation-Selective Ultraviolet-Ultraviolet Hole Burning Spectra of Ubiquitin Ions in a Cryogenic Ion Trap. J Phys Chem Lett 2024; 15:7398-7402. [PMID: 38995855 DOI: 10.1021/acs.jpclett.4c01385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/14/2024]
Abstract
Understanding the structural variations of conformational isomers in proteins is crucial for elucidating protein folding mechanisms. Here, we present a novel method for obtaining conformation-selective ultraviolet (UV)-UV hole burning (HB) spectra of ubiquitin ions ((Ubi+zH)+z, z = 7-10) produced via electrospray ionization. Our approach involves binding multiple N2 molecules to ubiquitin ions ((Ubi+zH)+z(N2)m, m = 1-55) within a cryogenic ion trap. Upon exposure to UV irradiation, efficient fragmentation of (Ubi+zH)+z(N2)m occurs, primarily yielding bare (Ubi+zH)+z ions as fragments. The significant mass difference between the parent and fragment ions facilitates the acquisition of UV-UV HB spectra, which reveal the presence of at least two distinct conformers. Molecular dynamics simulations suggest that these conformers correspond to A-state structures, differing only in the interactions of a tyrosine residue with neighboring residues. Our findings underscore UV-UV HB spectroscopy of protein ions as a powerful tool for exploring diverse protein isomers.
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Affiliation(s)
- Il Tae Yoo
- Department of Chemistry, Chungbuk National University, Chungbuk 28644, Korea
| | - Jinho Jeong
- Department of Chemistry, Chungbuk National University, Chungbuk 28644, Korea
| | - Han Jun Eun
- Gas Metrology Group, Division of Chemical and Biological Metrology, Korea Research Institute of Standards and Science (KRISS), Daejeon 34113, Korea
| | - Jiyeon Yun
- Department of Chemistry, Chungbuk National University, Chungbuk 28644, Korea
| | - Jiyoung Heo
- Department of Green Chemical Engineering, Sangmyung University, Chungnam 31066, Korea
| | - Nam Joon Kim
- Department of Chemistry, Chungbuk National University, Chungbuk 28644, Korea
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4
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Kang WY, Mondal A, Bonney JR, Perez A, Prentice BM. Structural Elucidation of Ubiquitin via Gas-Phase Ion/Ion Cross-Linking Reactions Using Sodium-Cationized Reagents Coupled with Infrared Multiphoton Dissociation. Anal Chem 2024; 96:8518-8527. [PMID: 38711366 PMCID: PMC11161031 DOI: 10.1021/acs.analchem.4c00442] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Accurate structural determination of proteins is critical to understanding their biological functions and the impact of structural disruption on disease progression. Gas-phase cross-linking mass spectrometry (XL-MS) via ion/ion reactions between multiply charged protein cations and singly charged cross-linker anions has previously been developed to obtain low-resolution structural information on proteins. This method significantly shortens experimental time relative to conventional solution-phase XL-MS but has several technical limitations: (1) the singly deprotonated N-hydroxysulfosuccinimide (sulfo-NHS)-based cross-linker anions are restricted to attachment at neutral amine groups of basic amino acid residues and (2) analyzing terminal cross-linked fragment ions is insufficient to unambiguously localize sites of linker attachment. Herein, we demonstrate enhanced structural information for alcohol-denatured A-state ubiquitin obtained from an alternative gas-phase XL-MS approach. Briefly, singly sodiated ethylene glycol bis(sulfosuccinimidyl succinate) (sulfo-EGS) cross-linker anions enable covalent cross-linking at both ammonium and amine groups. Additionally, covalently modified internal fragment ions, along with terminal b-/y-type counterparts, improve the determination of linker attachment sites. Molecular dynamics simulations validate experimentally obtained gas-phase conformations of denatured ubiquitin. This method has identified four cross-linking sites across 8+ ubiquitin, including two new sites in the N-terminal region of the protein that were originally inaccessible in prior gas-phase XL approaches. The two N-terminal cross-linking sites suggest that the N-terminal half of ubiquitin is more compact in gas-phase conformations. By comparison, the two C-terminal linker sites indicate the signature transformation of this region of the protein from a native to a denatured conformation. Overall, the results suggest that the solution-phase secondary structures of the A-state ubiquitin are conserved in the gas phase. This method also provides sufficient sensitivity to differentiate between two gas-phase conformers of the same charge state with subtle structural variations.
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Affiliation(s)
| | - Arup Mondal
- Department of Chemistry, University of Florida
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5
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Zviagin A, Boyarkin OV. Ion Spectroscopy Reveals Structural Difference for Proteins Microhydrated by Retention and Condensation of Water. J Phys Chem A 2024. [PMID: 38489273 DOI: 10.1021/acs.jpca.4c00263] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/17/2024]
Abstract
Protein ubiquitin in its +7 charge state microhydrated by 5 and 10 water molecules has been interrogated in the gas phase by cold ion UV/IR spectroscopy. The complexes were formed either by condensing water onto the unfolded bare proteins in a temperature-controlled ion trap or by incomplete dehydration of the folded proteins. In the case of cryogenic condensation, the UV spectra of the complexes exhibit a resolved vibrational structure, which looks similar to the spectrum of bare unfolded ubiquitin. The spectra become, however, broad-band with no structure when complexes of the same size are produced by incomplete dehydration under soft conditions of electrospray ionization. We attribute this spectroscopic dissimilarity to the structural difference of the protein: condensing a few water molecules cannot refold the gas-phase structure of the bare ubiquitin, while the retained water preserves its solution-like folded motif through evaporative cooling. This assessment is firmly confirmed by IR spectroscopy, which reveals the presence of free NH and carboxylic OH stretching vibrations only in the complexes with condensed water.
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Affiliation(s)
- Andrei Zviagin
- SCI-SB-RB Group, ISIC, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - Oleg V Boyarkin
- SCI-SB-RB Group, ISIC, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
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6
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Pan H, Raab SA, El-Baba TJ, Schrecke SR, Laganowsky A, Russell DH, Clemmer DE. Variation of CI-2 Conformers upon Addition of Methanol to Water: An IMS-MS-Based Thermodynamic Analysis. J Phys Chem A 2023; 127:9399-9408. [PMID: 37934510 PMCID: PMC11212803 DOI: 10.1021/acs.jpca.3c03651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
Abstract
Chymotrypsin inhibitor 2 (CI-2) is a well-studied, textbook example of a cooperative, two-state, native ↔ denatured folding transition. A recent hybrid ion mobility spectrometry (IMS)/mass spectrometry (MS) thermal denaturation study of CI-2 (the well-studied truncated 64-residue model) in water reported evidence that this two-state transition involves numerous (∼41) unique native and non-native (denatured) solution conformations. The characterization of so many, often low-abundance, states is possible because of the very high dynamic range of IMS-MS measurements of ionic species that are produced upon electrospraying CI-2 solutions from a variable temperature electrospray ionization source. A thermodynamic analysis of these states revealed large changes in enthalpy (ΔH) and entropy (ΔS) at different temperatures, and it was suggested that such variation might arise because of temperature-dependent conformational changes of the protein in response to changes in the conformational entropy and the dielectric permeability of water, which drops from a value of ε ∼ 79 at 24 °C to ∼ 60 at 82 °C. Herein, we examine how adding methanol to water influences the distributions of CI-2 conformers and their ensuing stabilities. The dielectric constant of a 60:40 water:methanol (MeOH) drops from ε ∼ 60 at 24 °C to ∼ 51 at 64 °C. Although the same set of conformers observed in water appears to be present in 60:40 water:MeOH, the abundance of each is substantially altered by the presence of methanol. Relative free energy values (ΔG) and thermodynamic values [ΔH and ΔS and heat capacities (ΔCp)] are derived from a Gibbs-Helmholtz analysis. A comparison of these data from water and water:MeOH systems allows rare insight into how variations in solvation and temperature affect many-state protein equilibria. While these studies confirm that variations in solvent dielectric constant with temperature affect the distributions of conformers that are observed, our findings suggest that other solvent differences may also affect abundances.
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Affiliation(s)
- Hua Pan
- 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
| | - Tarick J El-Baba
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, Indiana 47401, United States
| | - Samantha R Schrecke
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, 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
| | - David E Clemmer
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, Indiana 47401, United States
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7
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Sharif D, Rahman M, Mahmud S, Sultana MN, Attanayake K, DeBastiani A, Foroushani SH, Li P, Valentine SJ. In-droplet hydrogen-deuterium exchange to examine protein/peptide solution conformer heterogeneity. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2023; 37:e9593. [PMID: 37430450 PMCID: PMC10348485 DOI: 10.1002/rcm.9593] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 04/25/2023] [Accepted: 05/22/2023] [Indexed: 07/12/2023]
Abstract
RATIONALE Many different structure analysis techniques are not capable of probing the heterogeneity of solution conformations. Here, we examine the ability of in-droplet hydrogen-deuterium exchange (HDX) to directly probe solution conformer heterogeneity of a protein with mass spectrometry (MS) detection. METHODS Two vibrating capillary vibrating sharp-edge spray ionization (cVSSI) devices have been arranged such that they generate microdroplet plumes of the analyte and D2 O reagent, which coalesce to form reaction droplets where HDX takes place in the solution environment. The native HDX-MS setup has been first explored for two model peptides that have distinct structural compositions in solution. The effectiveness of the multidevice cVSSI-HDX in illustrating structural details has been further exploited to investigate coexisting solution-phase conformations of the protein ubiquitin. RESULTS In-droplet HDX reveals decreased backbone exchange for a model peptide that has a greater helix-forming propensity. Differences in intrinsic rates of the alanine and serine residues may account for much of the observed protection. The data allow the first estimates of backbone exchange rates for peptides undergoing in-droplet HDX. That said, the approach may hold greater potential for investigating the tertiary structure and structural transitions of proteins. For ubiquitin protein, HDX reactivity differences suggest that multiple conformers are present in native solutions. The addition of methanol to buffered aqueous solutions of ubiquitin results in increased populations of solution conformers of higher reactivity. Data analysis suggests that partially folded conformers such as the A-state of ubiquitin increase with methanol content; the native state may be preserved to a limited degree even under stronger denaturation conditions. CONCLUSION The deuterium uptake after in-droplet HDX has been observed to correspond to some degree with peptide backbone hydrogen protection based on differences in intrinsic rates of exchange. The presence of coexisting protein solution structures under native and denaturing solution conditions has been distinguished by the isotopic distributions of deuterated ubiquitin ions.
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Affiliation(s)
- Daud Sharif
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, USA
| | - Mohammad Rahman
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, USA
| | - Sultan Mahmud
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, USA
| | - Mst Nigar Sultana
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, USA
| | - Kushani Attanayake
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, USA
| | - Anthony DeBastiani
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, USA
| | - Samira Hajian Foroushani
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, USA
| | - Peng Li
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, USA
| | - Stephen J Valentine
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, West Virginia, USA
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8
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Sharon EM, Henderson LW, Clemmer DE. Resolving Hidden Solution Conformations of Hemoglobin Using IMS-IMS on a Cyclic Instrument. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:1559-1568. [PMID: 37418419 PMCID: PMC10916761 DOI: 10.1021/jasms.3c00032] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/09/2023]
Abstract
Ion mobility spectrometry-mass spectrometry (IMS-MS) experiments on a cyclic IMS instrument were used to examine heterogeneous distributions of structures found in the 15+ to 18+ charge states of the hemoglobin tetramer (Hb). The resolving power of IMS measurements is known to increase with increasing drift-region length. This effect is not significant for Hb charge states as peaks were shown to broaden with increasing drift-region length. This observation suggests that multiple structures with similar cross sections may be present. To examine this hypothesis, selections of drift time distributions were isolated and subsequently reinjected into the mobility region for additional separation. These IMS-IMS experiments demonstrate that selected regions separate further upon additional passes around the drift cell, consistent with the idea that initial resolving power was limited due to the presence of many closely related conformations. Additional variable temperature electrospray ionization (vT-ESI) experiments were conducted to study how changing the solution temperature affects solution conformations. Some features in these IMS-IMS studies were observed to change similarly with solution temperature compared to features in the single IMS distribution. Other features changed differently in the selected mobility data, indicating that solution structures that were obscured upon IMS analysis because of the complex heterogeneity of the original distribution are discernible after reducing the number of conformers that are analyzed by further IMS analysis. These results illustrate that the combination of vT-ESI with IMS-IMS is useful for resolving and exploring conformer distributions and stabilities in systems that exhibit a large degree of structural heterogeneity.
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Affiliation(s)
- Edie M Sharon
- Department of Chemistry, Indiana University Bloomington, Bloomington, Indiana 47405, United States
| | - Lucas W Henderson
- Department of Chemistry, Indiana University Bloomington, Bloomington, Indiana 47405, United States
| | - David E Clemmer
- Department of Chemistry, Indiana University Bloomington, Bloomington, Indiana 47405, United States
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9
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Christofi E, Barran P. Ion Mobility Mass Spectrometry (IM-MS) for Structural Biology: Insights Gained by Measuring Mass, Charge, and Collision Cross Section. Chem Rev 2023; 123:2902-2949. [PMID: 36827511 PMCID: PMC10037255 DOI: 10.1021/acs.chemrev.2c00600] [Citation(s) in RCA: 43] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Indexed: 02/26/2023]
Abstract
The investigation of macromolecular biomolecules with ion mobility mass spectrometry (IM-MS) techniques has provided substantial insights into the field of structural biology over the past two decades. An IM-MS workflow applied to a given target analyte provides mass, charge, and conformation, and all three of these can be used to discern structural information. While mass and charge are determined in mass spectrometry (MS), it is the addition of ion mobility that enables the separation of isomeric and isobaric ions and the direct elucidation of conformation, which has reaped huge benefits for structural biology. In this review, where we focus on the analysis of proteins and their complexes, we outline the typical features of an IM-MS experiment from the preparation of samples, the creation of ions, and their separation in different mobility and mass spectrometers. We describe the interpretation of ion mobility data in terms of protein conformation and how the data can be compared with data from other sources with the use of computational tools. The benefit of coupling mobility analysis to activation via collisions with gas or surfaces or photons photoactivation is detailed with reference to recent examples. And finally, we focus on insights afforded by IM-MS experiments when applied to the study of conformationally dynamic and intrinsically disordered proteins.
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Affiliation(s)
- Emilia Christofi
- Michael Barber Centre for Collaborative
Mass Spectrometry, Manchester Institute of Biotechnology, University of Manchester, Princess Street, Manchester M1 7DN, United Kingdom
| | - Perdita Barran
- Michael Barber Centre for Collaborative
Mass Spectrometry, Manchester Institute of Biotechnology, University of Manchester, Princess Street, Manchester M1 7DN, United Kingdom
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10
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Li W, Chaihu L, Jiang J, Wu B, Zheng X, Dai R, Tian Y, Huang Y, Wang G, Men Y. Microfluidic Platform for Time-Resolved Characterization of Protein Higher-Order Structures and Dynamics Using Top-Down Mass Spectrometry. Anal Chem 2022; 94:7520-7527. [PMID: 35584038 DOI: 10.1021/acs.analchem.2c00077] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Characterization of protein higher-order structures and dynamics is essential for understanding the biological functions of proteins and revealing the underlying mechanisms. Top-down mass spectrometry (MS) accesses structural information at both the intact protein level and the peptide fragment level. Native top-down MS allows analysis of a protein complex's architecture and subunits' identity and modifications. Top-down hydrogen/deuterium exchange (HDX) MS offers high spatial resolution for conformational or binding interface analysis and enables conformer-specific characterization. A microfluidic chip can provide superior performance for front-end reactions useful for these MS workflows, such as flexibility in manipulating multiple reactant flows, integrating various functional modules, and automation. However, most microchip-MS devices are designed for bottom-up approaches or top-down proteomics. Here, we demonstrate a strategy for designing a microchip for top-down MS analysis of protein higher-order structures and dynamics. It is suitable for time-resolved native MS and HDX MS, with designs aiming for efficient ionization of intact protein complexes, flexible manipulation of multiple reactant flows, and precise control of reaction times over a broad range of flow rates on the submicroliter per minute scale. The performance of the prototype device is demonstrated by measurements of systems including monoclonal antibodies, antibody-antigen complexes, and coexisting protein conformers. This strategy may benefit elaborate structural analysis of biomacromolecules and inspire method development using the microchip-MS approach.
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Affiliation(s)
- Wen Li
- Research Center for Biomedical Optics and Molecular Imaging, Institute of Biomedical and Health Engineering, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Lingxiao Chaihu
- School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, China.,Institute of Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China
| | - Jialu Jiang
- School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, China
| | - Bizhu Wu
- Research Center for Biomedical Optics and Molecular Imaging, Institute of Biomedical and Health Engineering, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Xuan Zheng
- Research Center for Biomedical Optics and Molecular Imaging, Institute of Biomedical and Health Engineering, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
| | - Rongrong Dai
- School of Chemistry and Materials Science, Nanjing Normal University, Nanjing 210023, China
| | - Ye Tian
- Institute of Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China
| | - Yanyi Huang
- Institute of Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China.,Biomedical Pioneering Innovation Centre, Peking University, Beijing 100871, China
| | - Guanbo Wang
- Institute of Cell Analysis, Shenzhen Bay Laboratory, Shenzhen 518132, China.,Biomedical Pioneering Innovation Centre, Peking University, Beijing 100871, China
| | - Yongfan Men
- Research Center for Biomedical Optics and Molecular Imaging, Institute of Biomedical and Health Engineering, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
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11
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Zviagin A, Kopysov V, Nagornova NS, Boyarkin OV. Tracking local and global structural changes in a protein by cold ion spectroscopy. Phys Chem Chem Phys 2022; 24:8158-8165. [PMID: 35332911 DOI: 10.1039/d2cp00217e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Characterization of native structures of proteins in the gas phase remains challenging due to the unpredictable conformational changes the molecules undergo during desolvation and ionization. We spectroscopically studied cryogenically cooled protonated protein ubiquitin and its microhydrated complexes prepared in the gas phase in a range of charge states under different ionization conditions. The UV spectra appear vibrationally resolved for the unfolded protein, but become redshifted and smooth for the native-like structures of ubiquitin. This spectroscopic change results from the H-bonding of the hydroxyl of Tyr to the amide group of Glu-51 in the compact structures; the minimum length of this bond was estimated to be ∼1.7 Å. IR spectroscopy reflects the global structural change by observing redshifts of free NH/OH-stretch vibrational transitions. Evaporative cooling of microhydrated complexes of ubiquitin keeps the protein chilly during ionization, enabling native-like conformers with up to eight protons to survive in the gas phase.
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Affiliation(s)
- Andrei Zviagin
- Laboratoire de Chimie Physique Moléculaire, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
| | - Vladimir Kopysov
- Laboratoire de Chimie Physique Moléculaire, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
| | - Natalia S Nagornova
- Laboratoire de Chimie Physique Moléculaire, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
| | - Oleg V Boyarkin
- Laboratoire de Chimie Physique Moléculaire, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland.
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12
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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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13
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Cheung See Kit M, Shepherd SO, Prell JS, Webb IK. Experimental Determination of Activation Energies for Covalent Bond Formation via Ion/Ion Reactions and Competing Processes. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:2313-2321. [PMID: 33730481 PMCID: PMC9248411 DOI: 10.1021/jasms.1c00025] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The combination of ion/ion chemistry with commercially available ion mobility/mass spectrometry systems has allowed rich structural information to be obtained for gaseous protein ions. Recently, the simple modification of such an instrument with an electrospray reagent source has allowed three-dimensional gas-phase interrogation of protein structures through covalent and noncovalent interactions coupled with collision cross section measurements. However, the energetics of these processes have not yet been studied quantitatively. In this work, previously developed Monte Carlo simulations of ion temperatures inside traveling wave ion guides are used to characterize the energetics of the transition state of activated ubiquitin cation/sulfo-benzoyl-HOAt reagent anion long-lived complexes formed via ion/ion reactions. The ΔH‡ and ΔS‡ of major processes observed from collisional activation of long-lived gas-phase ion/ion complexes, namely collision induced unfolding (CIU), covalent bond formation, or neutral loss of the anionic reagent via intramolecular proton transfer, were determined. Covalent bond formation via ion/ion complexes was found to be significantly lower energy compared to unfolding and bond cleavage. The ΔG‡ values of activation of all three processes lie between 55 and 75 kJ/mol, easily accessible with moderate collisional activation. Bond formation is favored over reagent loss at lower activation energies, whereas reagent loss becomes competitive at higher collision energies. Though the ΔG‡ values between CIU of a precursor ion and covalent bond formation of its ion/ion product complex are comparable, our data suggest covalent bond formation does not require extensive isomerization.
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Affiliation(s)
- Melanie Cheung See Kit
- Department of Chemistry and Chemical Biology, Indiana University Purdue University Indianapolis, Indianapolis, Indiana 46202, USA
| | - Samantha O. Shepherd
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, USA
| | - James S. Prell
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, USA
- Materials Science Institute, University of Oregon, Eugene, OR 97403, USA
| | - Ian K. Webb
- Department of Chemistry and Chemical Biology, Indiana University Purdue University Indianapolis, Indianapolis, Indiana 46202, USA
- Center for Computational Biology and Bioinformatics, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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14
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Raab SA, El-Baba TJ, Laganowsky A, Russell DH, Valentine SJ, Clemmer DE. Protons Are Fast and Smart; Proteins Are Slow and Dumb: On the Relationship of Electrospray Ionization Charge States and Conformations. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:1553-1561. [PMID: 34151568 PMCID: PMC9003666 DOI: 10.1021/jasms.1c00100] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We present simple considerations of how differences in time scales of motions of protons, the lightest and fastest chemical moiety, and the much longer time scales associated with the dynamics of proteins, among the heaviest and slowest analytes, may allow many protein conformations from solution to be kinetically trapped during the process of electrospraying protein solutions into the gas phase. In solution, the quantum nature of protons leads them to change locations by tunneling, an instantaneous process; moreover, the Grotthuss mechanism suggests that these small particles can respond nearly instantaneously to the dynamic motions of proteins that occur on much longer time scales. A conformational change is accompanied by favorable or unfavorable variations in the free energy of the system, providing the impetus for solvent ↔ protein proton exchange. Thus, as thermal distributions of protein conformations interconvert, protonation states rapidly respond, as specific acidic and basic sites are exposed or protected. In the vacuum of the mass spectrometer, protons become immobilized in locations that are specific to the protein conformations from which they were incorporated. In this way, conformational states from solution are preserved upon electrospraying them into the gas phase. These ideas are consistent with the exquisite sensitivity of electrospray mass spectra to small changes of the local environment that alter protein structure in solution. We might remember this approximation for the protonation of proteins in solution with the colloquial expression-protons are fast and smart; proteins are slow and dumb.
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Affiliation(s)
- Shannon A Raab
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Tarick J El-Baba
- 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
| | - Stephen J Valentine
- Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506, United States
| | - David E Clemmer
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
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15
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Kit MCS, Carvalho VV, Vilseck JZ, Webb IK. Gas-Phase Ion/Ion Chemistry for Structurally Sensitive Probes of Gaseous Protein Ion Structure: Electrostatic and Electrostatic to Covalent Cross-Linking. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2021; 463:116549. [PMID: 33716558 PMCID: PMC7946065 DOI: 10.1016/j.ijms.2021.116549] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Intramolecular interactions within a protein are key in maintaining protein tertiary structure and understanding how proteins function. Ion mobility-mass spectrometry (IM-MS) has become a widely used approach in structural biology since it provides rapid measurements of collision cross sections (CCS), which inform on the gas-phase conformation of the biomolecule under study. Gas-phase ion/ion reactions target amino acid residues with specific chemical properties and the modified sites can be identified by MS. In this study, electrostatically reactive, gas-phase ion/ion chemistry and IM-MS are combined to characterize the structural changes between ubiquitin electrosprayed from aqueous and denaturing conditions. The electrostatic attachment of sulfo-NHS acetate to ubiquitin via ion/ion reactions and fragmentation by electron-capture dissociation (ECD) provide the identification of the most accessible protonated sites within ubiquitin as the sulfonate group forms an electrostatic complex with accessible protonated side chains. The protonated sites identified by ECD from the different solution conditions are distinct and, in some cases, reflect the disruption of interactions such as salt bridges that maintain the native protein structure. This agrees with previously published literature demonstrating that a high methanol concentration at low pH causes the structure of ubiquitin to change from a native (N) state to a more elongated A state. Results using gas-phase, electrostatic cross-linking reagents also point to similar structural changes and further confirm the role of methanol and acid in favoring a more unfolded conformation. Since cross-linking reagents have a distance constraint for the two reactive sites, the data is valuable in guiding computational structures generated by molecular dynamics. The research presented here describes a promising strategy that can detect subtle changes in the local environment of targeted amino acid residues to inform on changes in the overall protein structure.
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Affiliation(s)
- Melanie Cheung See Kit
- Department of Chemistry and Chemical Biology, Indiana University Purdue University Indianapolis, Indianapolis, Indiana 46202, USA
| | - Veronica V. Carvalho
- Department of Chemistry and Chemical Biology, Indiana University Purdue University Indianapolis, Indianapolis, Indiana 46202, USA
| | - Jonah Z. Vilseck
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
- Center for Computational Biology and Bioinformatics, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
| | - Ian K. Webb
- Department of Chemistry and Chemical Biology, Indiana University Purdue University Indianapolis, Indianapolis, Indiana 46202, USA
- Center for Computational Biology and Bioinformatics, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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16
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Raab SA, El-Baba TJ, Woodall DW, Liu W, Liu Y, Baird Z, Hales DA, Laganowsky A, Russell DH, Clemmer DE. Evidence for Many Unique Solution Structures for Chymotrypsin Inhibitor 2: A Thermodynamic Perspective Derived from vT-ESI-IMS-MS Measurements. J Am Chem Soc 2020; 142:17372-17383. [PMID: 32866376 DOI: 10.1021/jacs.0c05365] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Chymotrypsin inhibitor 2 (CI-2) is a classic model for two-state cooperative protein folding and is one of the most extensively studied systems. Alan Fersht, a pioneer in the field of structural biology, has studied the wild-type (wt) and over 100 mutant forms of CI-2 with traditional analytical and biochemical techniques. Here, we examine wt CI-2 and three mutant forms (A16G, K11A, L32A) to demonstrate the utility of variable-temperature (vT) electrospray ionization (ESI) paired with ion mobility spectrometry (IMS) and mass spectrometry (MS) to map the free energy folding landscape. As the solution temperature is increased, the abundance of each of the six ESI charge states for wt CI-2 and each mutant is found to vary independently. These results require that at least six unique types of CI-2 solution conformers are present. Ion mobility analysis reveals that within each charge state there are additional conformers having distinct solution temperature profiles. A model of the data at ∼30 different temperatures for all four systems suggests the presence of 41 unique CI-2 solution conformations. A thermodynamic analysis of this system yields values of ΔCp as well as ΔG, ΔH, and ΔS for each state at every temperature studied. Detailed energy landscapes derived from these data provide a rare glimpse into Anfinsen's thermodynamic hypothesis and the process of thermal denaturation, normally thought of as a cooperative two-state transition involving the native state and unstructured denatured species. Specifically, as the temperature is varied, the entropies and enthalpies of different conformers undergo dramatic changes in magnitude and relative order to maintain the delicate balance associated with equilibrium.
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Affiliation(s)
- Shannon A Raab
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, Indiana 47401, United States
| | - Tarick J El-Baba
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, Indiana 47401, United States
| | - Daniel W Woodall
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, Indiana 47401, United States
| | - Wen Liu
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Yang Liu
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
| | - Zane Baird
- Baxter Healthcare Corporation, 927 South Curry Pike, Bloomington, Indiana 47403, United States
| | - David A Hales
- Department of Chemistry, Hendrix College, Conway, Arkansas 72032, 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
| | - David E Clemmer
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, Indiana 47401, United States
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17
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Jeanne Dit Fouque K, Fernandez-Lima F. Following Structural Changes by Thermal Denaturation Using Trapped Ion Mobility Spectrometry-Mass Spectrometry. J Phys Chem B 2020; 124:6257-6265. [PMID: 32560586 PMCID: PMC8341290 DOI: 10.1021/acs.jpcb.0c04276] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The behavior of biomolecules as a function of the solution temperature is often crucial to assessing their biological activity and function. While heat-induced changes of biomolecules are traditionally monitored using optical spectroscopy methods, their conformational changes and unfolding transitions remain challenging to interpret. In the present work, the structural transitions of bovine serum albumin (BSA) in native conditions (100 mM aqueous ammonium acetate) were investigated as a function of the starting solution temperature (T ∼ 23-70 °C) using a temperature-controlled nanoelectrospray ionization source (nESI) coupled to a trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) instrument. The charge state distribution of the monomeric BSA changed from a native-like, narrow charge state ([M + 12H]12+ to [M + 16H]16+ at ∼23 °C) and narrow mobility distribution toward an unfolded-like, broad charge state (up to [M + 46H]46+ at ∼70 °C) and broad mobility distribution. Inspection of the average charge state and collision cross section (CCS) distribution suggested a two-state unfolding transition with a melting temperature Tm ∼ 56 ± 1 °C; however, the inspection of the CCS profiles at the charge state level as a function of the solution temperature showcases at least six structural transitions (T1-T7). If the starting solution concentration is slightly increased (from 2 to 25 μM), this method can detect nonspecific BSA dimers and trimers which dissociate early (Td ∼ 34 ± 1 °C) and may disturb the melting curve of the BSA monomer. In a single experiment, this technology provides a detailed view of the solution, protein structural landscape (mobility vs solution temperature vs relative intensity for each charge state).
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Affiliation(s)
- Kevin Jeanne Dit Fouque
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
| | - Francisco Fernandez-Lima
- Department of Chemistry and Biochemistry, Florida International University, Miami, Florida 33199, United States
- Biomolecular Sciences Institute, Florida International University, Miami, Florida 33199, United States
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18
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Zheng X, Kurulugama RT, Laganowsky A, Russell DH. Collision-Induced Unfolding Studies of Proteins and Protein Complexes using Drift Tube Ion Mobility-Mass Spectrometer. Anal Chem 2020; 92:7218-7225. [PMID: 32338885 DOI: 10.1021/acs.analchem.0c00772] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Elucidating the structures and stabilities of proteins and their complexes is paramount to understanding their biological functions in cellular processes. Native mass spectrometry (MS) coupled with ion mobility spectrometry (IMS) is emerging as an important biophysical technique owing to its high sensitivity, rapid analysis time, and ability to interrogate sample complexity or heterogeneity and the ability to probe protein structure dynamics. Here, a commercial IMS-MS platform has been modified for static native ESI emitters and an extended mass-to-charge range (20 kDa m/z) and its performance capabilities and limits were explored for a range of protein and protein complexes. The results show new potential for this instrument platform for studies of large protein and protein complexes and provides a roadmap for extending the performance metrics for studies of even larger, more complex systems, namely, membrane protein complexes and their interactions with ligands.
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Affiliation(s)
- Xueyun Zheng
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, 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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19
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Carvalho VV, Cheung See Kit M, Webb IK. Ion Mobility and Gas-Phase Covalent Labeling Study of the Structure and Reactivity of Gaseous Ubiquitin Ions Electrosprayed from Aqueous and Denaturing Solutions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2020; 31:1037-1046. [PMID: 32255627 PMCID: PMC7205579 DOI: 10.1021/jasms.9b00138] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Gas-phase ion/ion chemistry was coupled to ion mobility/mass spectrometry analysis to correlate the structure of gaseous ubiquitin to its solution structures with selective covalent structural probes. Collision cross section (CCS) distributions were measured to ensure the ubiquitin ions were not unfolded when they were introduced to the gas phase. Aqueous solutions stabilizing the native state of ubiquitin yielded folded ubiquitin structures with CCS values consistent with previously published literature. Denaturing solutions favored several families of unfolded conformations for most of the charge states evaluated. Gas-phase covalent labeling via ion/ion reactions was followed by collision-induced dissociation of the intact, labeled protein to determine which residues were labeled. Ubiquitin 5+ and 6+ electrosprayed from aqueous conditions were covalently modified preferentially at the lysine 29 and arginine 54 positions, indicating that elements of three-dimensional structure were maintained in the gas phase. On the other hand, most ubiquitin ions produced in denaturing conditions were labeled at various other lysine residues, likely due to the availability of additional sites following methanol- and low-pH-induced unfolding. These data support the conservation of ubiquitin structural elements in the gas phase. The research presented here provides the basis for residue-specific characterization of biomolecules in the gas phase.
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Affiliation(s)
| | | | - Ian K. Webb
- Indiana University Purdue University Indianapolis, Indianapolis, IN, USA 46202
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20
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Brodbelt JS, Morrison LJ, Santos I. Ultraviolet Photodissociation Mass Spectrometry for Analysis of Biological Molecules. Chem Rev 2020; 120:3328-3380. [PMID: 31851501 PMCID: PMC7145764 DOI: 10.1021/acs.chemrev.9b00440] [Citation(s) in RCA: 139] [Impact Index Per Article: 34.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The development of new ion-activation/dissociation methods continues to be one of the most active areas of mass spectrometry owing to the broad applications of tandem mass spectrometry in the identification and structural characterization of molecules. This Review will showcase the impact of ultraviolet photodissociation (UVPD) as a frontier strategy for generating informative fragmentation patterns of ions, especially for biological molecules whose complicated structures, subtle modifications, and large sizes often impede molecular characterization. UVPD energizes ions via absorption of high-energy photons, which allows access to new dissociation pathways relative to more conventional ion-activation methods. Applications of UVPD for the analysis of peptides, proteins, lipids, and other classes of biologically relevant molecules are emphasized in this Review.
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Affiliation(s)
- Jennifer S. Brodbelt
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Lindsay J. Morrison
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Inês Santos
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
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21
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Brown CJ, Woodall DW, El-Baba TJ, Clemmer DE. Characterizing Thermal Transitions of IgG with Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:2438-2445. [PMID: 31363989 PMCID: PMC6866664 DOI: 10.1007/s13361-019-02292-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 07/15/2019] [Accepted: 07/16/2019] [Indexed: 06/02/2023]
Abstract
Variable temperature electrospray ionization (ESI) is coupled with mass spectrometry techniques in order to investigate structural transitions of monoclonal antibody immunoglobulin G (IgG) in a 100-mM ammonium acetate (pH 7.0) solution from 26 to 70 °C. At 26 °C, the mass spectrum for intact IgG shows six charge states + 22 to + 26. Upon increasing the solution temperature, the fraction of low-charge states decreases and new, higher-charge state ions are observed. Upon analysis, it appears that heating the solution aids in desolvation of the intact IgG precursor. Above ~ 50 °C, a cleavage event between the light and heavy chains is observed. An analysis of the kinetics for these processes at different temperatures yields transition state thermochemistry of ΔH‡ = 95 ± 10 kJ mol-1, ΔS‡ = 8 ± 1 J mol-1 K-1, and ΔG‡ = 92 ± 11 kJ mol-1. The mechanism for light chain dissociation appears to involve disulfide bond scrambling that ultimately results in a non-native Cys199-Cys217 disulfide bond in the light chain product. Above ~ 70 °C, we are unable to produce a stable ESI signal. The loss of signal is ascribed to aggregation that is primarily associated with the remaining portion of the antibody after having lost the light chain. Graphical Abstract.
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Affiliation(s)
- Christopher J Brown
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, IN, 47401, USA
| | - Daniel W Woodall
- 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
| | - David E Clemmer
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, IN, 47401, USA.
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22
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Illes-Toth E, Cooper HJ. Probing the Fundamentals of Native Liquid Extraction Surface Analysis Mass Spectrometry of Proteins: Can Proteins Refold during Extraction? Anal Chem 2019; 91:12246-12254. [PMID: 31490666 PMCID: PMC7006963 DOI: 10.1021/acs.analchem.9b02075] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Native ambient mass spectrometry has the potential for simultaneous analysis of native protein structure and spatial distribution within thin tissue sections. Notwithstanding sensitivity, this information can, in principle, be obtained for any protein present with no requirement for a priori knowledge of protein identity. To date, native ambient mass spectrometry has primarily made use of the liquid extraction surface analysis (LESA) sampling technique. Here, we address a fundamental question: Are the protein structures observed following native liquid extraction surface analysis representative of the protein structures within the substrate, or does the extraction process facilitate refolding (or unfolding)? Specifically, our aim was to determine whether protein-ligand complexes observed following LESA are indicative of complexes present in the substrate, or an artifact of the sampling process. The systems investigated were myoglobin and its noncovalently bound heme cofactor, and the Zn-binding protein carbonic anhydrase and its binding with ethoxzolamide. Charge state distributions, drift time profiles, and collision cross sections were determined by liquid extraction surface analysis ion mobility mass spectrometry of native and denatured proteins and compared with those obtained by direct infusion electrospray. The results show that it was not possible to refold denatured proteins with concomitant ligand binding (neither heme, zinc, nor ethoxzolamide) simply by use of native-like LESA solvents. That is, protein-ligand complexes were only observed by LESA MS when present in the substrate.
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Affiliation(s)
- Eva Illes-Toth
- School of Biosciences , University of Birmingham , Birmingham , B15 2TT , U.K
| | - Helen J Cooper
- School of Biosciences , University of Birmingham , Birmingham , B15 2TT , U.K
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23
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El-Baba TJ, Clemmer DE. Solution thermochemistry of concanavalin A tetramer conformers measured by variable-temperature ESI-IMS-MS. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2019; 443:93-100. [PMID: 32226278 PMCID: PMC7100878 DOI: 10.1016/j.ijms.2019.06.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Variable-temperature nano-electrospray ionization coupled with ion mobility spectrometry-mass spectrometry is used to investigate the thermal denaturation of the tetrameric protein concanavalin A. As the solution temperature is increased, changes in mass spectra and collision cross section distributions provide evidence for discrete structural changes that occur at temperatures that are ~40 to 50 degrees below the temperature required for tetramer dissociation. The subtle structural changes are associated with four distinct tetramer conformations with unique melting temperatures. Gibbs-Helmholtz analysis of the free energies determined with respect to the most abundant "native" state yields heat capacities of ΔCp = 1.6 ± 0.3, -2.2 ± 0.4, and -2.9 ± 1.6 kJ·K-1·mol-1, and temperature dependent enthalpies and entropies for the three non-native conformations. Analysis of the thermochemistry indicates that the high-temperature products are entropically stable until the threshold for tetramer dissociation, and changes in heat capacity are consistent with increases in solvation of polar residues. Our findings suggest these high-temperature non-native states result from an increase in disorder at surface exposed regions. Such studies provide valuable insight towards the structural details of non-native states.
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Affiliation(s)
- Tarick J El-Baba
- Department of Chemistry, Indiana University, Bloomington IN, 47401 USA
| | - David E Clemmer
- Department of Chemistry, Indiana University, Bloomington IN, 47401 USA
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24
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Talbert LE, Zhang X, Hendricks N, Alizadeh A, Julian RR. Synthesis of New S-S and C-C Bonds by Photoinitiated Radical Recombination Reactions in the Gas Phase. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2019; 441:25-31. [PMID: 31607789 PMCID: PMC6788626 DOI: 10.1016/j.ijms.2019.04.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Photoinitiated radical chemistry has proven to be useful for breaking covalent bonds within many biomolecules in the gas phase. Herein, we demonstrate that radical chemistry is useful for bond synthesis in the gas phase. Single peptides containing two cysteine residues capped with propylmercaptan (PM) often form disulfide bonds following ultraviolet excitation at 266 nm and loss of both PM groups. Similarly, noncovalently bound peptide pairs where each peptide contains a single cysteine residue can be induced to form disulfide bonds. Comparison with disulfide bound species sampled directly from solution yields identical collisional activation spectra, suggesting that native disulfide bonds have been recapitulated in the gas phase syntheses. Another approach utilizing radical chemistry for covalent bond synthesis involves creation of a reactive diradical that can first abstract hydrogen from a target peptide, creating a new radical site, and then recombine the second radical with the new radical to form a covalent bond. This chemistry is illustrated with 2-(hydroxymethyl-3,5-diiodobenzoate)-18-crown-6 ether, which attaches noncovalently to protonated primary amines in peptides and proteins. Following photoactivation and crosslinking, the site of noncovalent adduct attachment can frequently be determined. The ramifications of these observations on peptide structure and noncovalent attachment of 18-crown-6-based molecules is discussed.
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25
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Hedison TM, Scrutton NS. Tripping the light fantastic in membrane redox biology: linking dynamic structures to function in ER electron transfer chains. FEBS J 2019; 286:2004-2017. [PMID: 30657259 PMCID: PMC6563164 DOI: 10.1111/febs.14757] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Revised: 12/16/2018] [Accepted: 01/15/2019] [Indexed: 12/19/2022]
Abstract
How the dynamics of proteins assist catalysis is a contemporary issue in enzymology. In particular, this holds true for membrane‐bound enzymes, where multiple structural, spectroscopic and biochemical approaches are needed to build up a comprehensive picture of how dynamics influence enzyme reaction cycles. Of note are the recent studies of cytochrome P450 reductases (CPR)–P450 (CYP) endoplasmic reticulum redox chains, showing the relationship between dynamics and electron flow through flavin and haem redox centres and the impact this has on monooxygenation chemistry. These studies have led to deeper understanding of mechanisms of electron flow, including the timing and control of electron delivery to protein‐bound cofactors needed to facilitate CYP‐catalysed reactions. Individual and multiple component systems have been used to capture biochemical behaviour and these have led to the emergence of more integrated models of catalysis. Crucially, the effects of membrane environment and composition on reaction cycle chemistry have also been probed, including effects on coenzyme binding/release, thermodynamic control of electron transfer, conformational coupling between partner proteins and vectorial versus ‘off pathway’ electron flow. Here, we review these studies and discuss evidence for the emergence of dynamic structural models of electron flow along human microsomal CPR–P450 redox chains.
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Affiliation(s)
- Tobias M Hedison
- Manchester Institute of Biotechnology and School of Chemistry, University of Manchester, UK
| | - Nigel S Scrutton
- Manchester Institute of Biotechnology and School of Chemistry, University of Manchester, UK
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26
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Poltash ML, McCabe JW, Patrick JW, Laganowsky A, Russell DH. Development and Evaluation of a Reverse-Entry Ion Source Orbitrap Mass Spectrometer. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:192-198. [PMID: 29796735 PMCID: PMC6251776 DOI: 10.1007/s13361-018-1976-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 04/16/2018] [Accepted: 04/17/2018] [Indexed: 05/08/2023]
Abstract
As a step towards development of a high-resolution ion mobility mass spectrometer using the orbitrap mass analyzer platform, we describe herein a novel reverse-entry ion source (REIS) coupled to the higher-energy C-trap dissociation (HCD) cell of an orbitrap mass spectrometer with extended mass range. Development of the REIS is a first step in the development of a drift tube ion mobility-orbitrap MS. The REIS approach retains the functionality of the commercial instrument ion source which permits the uninterrupted use of the instrument during development as well as performance comparisons between the two ion sources. Ubiquitin (8.5 kDa) and lipid binding to the ammonia transport channel (AmtB, 126 kDa) protein complex were used as model soluble and membrane proteins, respectively, to evaluate the performance of the REIS instrument. Mass resolution obtained with the REIS is comparable to that obtained using the commercial ion source. The charge state distributions for ubiquitin and AmtB obtained on the REIS are in agreement with previous studies which suggests that the REIS-orbitrap EMR retains native structure in the gas phase. Graphical Abstract ᅟ.
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Affiliation(s)
- Michael L Poltash
- Department of Chemistry, Texas A&M University, College Station, TX, 77843, USA
| | - Jacob W McCabe
- Department of Chemistry, Texas A&M University, College Station, TX, 77843, USA
| | - John W Patrick
- Department of Chemistry, Texas A&M University, College Station, TX, 77843, USA
| | - Arthur Laganowsky
- Department of Chemistry, Texas A&M University, College Station, TX, 77843, USA.
| | - David H Russell
- Department of Chemistry, Texas A&M University, College Station, TX, 77843, USA.
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27
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El-Baba TJ, Fuller DR, Hales DA, Russell DH, Clemmer DE. Solvent Mediation of Peptide Conformations: Polyproline Structures in Water, Methanol, Ethanol, and 1-Propanol as Determined by Ion Mobility Spectrometry-Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2019; 30:77-84. [PMID: 30069641 PMCID: PMC6503664 DOI: 10.1007/s13361-018-2034-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 07/03/2018] [Accepted: 07/07/2018] [Indexed: 05/30/2023]
Abstract
Ion mobility spectrometry and circular dichroism spectroscopy are used to examine the populations of the small model peptide, polyproline-13 in water, methanol, ethanol, and 1-propanol over a range of solution temperatures (from 288 to 318 K). At low temperatures, the less-polar solvents (1-propanol and ethanol) favor the all-cis polyproline I helix (PPI); as the temperature is increased, the trans-configured polyproline II helix (PPII) is formed. In polar solvents (methanol and water), PPII is favored at all temperatures. From the experimental data, we determine the relative stabilities of the eight structures in methanol, ethanol, and 1-propanol, as well as four in water, all with respect to PPII. Although these conformers show relatively small differences in free energies, substantial variability is observed in the enthalpies and entropies across the structures and solvents. This requires that enthalpies and entropies be highly correlated: in 1-propanol, cis-configured PPI conformations are energetically favorable but entropically disfavored. In more polar solvents, PPI is enthalpically less favorable and entropy favors trans-configured forms. While either ΔH0 or ΔS0 can favor different structures, no conformation in any solvent is simultaneously energetically and entropically stabilized. These data present a rare opportunity to examine the origin of conformational stability. Graphical Abstract ᅟ.
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Affiliation(s)
- Tarick J El-Baba
- 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
| | - David A Hales
- Department of Chemistry, Hendrix College, Conway, AR, 72032, 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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28
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May JC, Jurneczko E, Stow SM, Kratochvil I, Kalkhof S, McLean JA. Conformational Landscapes of Ubiquitin, Cytochrome c, and Myoglobin: Uniform Field Ion Mobility Measurements in Helium and Nitrogen Drift Gas. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2018; 427:79-90. [PMID: 29915518 PMCID: PMC6003721 DOI: 10.1016/j.ijms.2017.09.014] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
In this study, a commercial uniform field drift tube ion mobility-mass spectrometer (IM-MS) was utilized to measure the gas-phase conformational populations of three well-studied proteins: ubiquitin (8566 Da), cytochrome c (12,359 Da), and myoglobin in both apo and holo forms (16,951 and 17,567 Da, respectively) in order to evaluate the use of this technology for broadscale structural proteomics applications. Proteins were electrosprayed from either acidic organic (pH ~3) or aqueous buffered (pH ~6.6) solution phase conditions, which generated a wide range of cation charge states corresponding to both extended (unfolded) and compact (folded) gas-phase conformational populations. Corresponding collision cross section (CCS) measurements were compiled for significant ion mobility peak features observed at each charge state in order to map the conformational landscapes of these proteins in both helium and nitrogen drift gases. It was observed that the conformational landscapes were similar in both drift gases, with differences being attributed primarily to ion heating during helium operation due to the necessity of operating the instrument with higher pressure differentials. Higher resolving powers were observed in nitrogen, which allowed for slightly better structural resolution of closely-spaced conformer populations. The instrumentation was found to be particularly adept at measuring low abundance conformers which are only present under gentle conditions which minimize ion heating. This work represents the single largest ion mobility CCS survey published to date for these three proteins with 266 CCS values and 117 ion mobility spectra, many of which have not been previously reported.
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Affiliation(s)
- Jody C. May
- Department of Chemistry, Center for Innovative Technology, Vanderbilt Institute for Integrative Biosystems Research and Education, and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, 37235, United States
| | - Ewa Jurneczko
- Department of Chemistry, Center for Innovative Technology, Vanderbilt Institute for Integrative Biosystems Research and Education, and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, 37235, United States
| | - Sarah M. Stow
- Department of Chemistry, Center for Innovative Technology, Vanderbilt Institute for Integrative Biosystems Research and Education, and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, 37235, United States
| | - Isabel Kratochvil
- Institute of Biochemistry, Faculty of Biosciences, Pharmacy and Psychology, Leipzig University, 04103 Leipzig, Germany
| | - Stefan Kalkhof
- Department of Molecular Systems Biology, Helmholtz-Centre for Environmental Research - UFZ, 04318 Leipzig, Germany
| | - John A. McLean
- Department of Chemistry, Center for Innovative Technology, Vanderbilt Institute for Integrative Biosystems Research and Education, and Vanderbilt Institute of Chemical Biology, Vanderbilt University, Nashville, Tennessee, 37235, United States
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29
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El-Baba TJ, Fuller DR, Woodall DW, Raab SA, Conant CR, Dilger JM, Toker Y, Williams ER, Russell DH, Clemmer DE. Melting proteins confined in nanodroplets with 10.6 μm light provides clues about early steps of denaturation. Chem Commun (Camb) 2018; 54:3270-3273. [PMID: 29536995 PMCID: PMC5871606 DOI: 10.1039/c7cc09829d] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Ubiquitin confined within nanodroplets was irradiated with a variable-power CO2 laser. Mass spectrometry analysis shows evidence for a protein "melting"-like transition within droplets prior to solvent evaporation and ion formation. Ion mobility spectrometry reveals that structures associated with early steps of denaturation are trapped because of short droplet lifetimes.
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Affiliation(s)
- Tarick J El-Baba
- Department of Chemistry, Indiana University, 800 Kirkwood Avenue, Bloomington, Indiana, 47401, USA.
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30
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Morrison LJ, Chai W, Rosenberg JA, Henkelman G, Brodbelt JS. Characterization of hydrogen bonding motifs in proteins: hydrogen elimination monitoring by ultraviolet photodissociation mass spectrometry. Phys Chem Chem Phys 2018; 19:20057-20074. [PMID: 28722742 DOI: 10.1039/c7cp04073c] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Determination of structure and folding of certain classes of proteins remains intractable by conventional structural characterization strategies and has spurred the development of alternative methodologies. Mass spectrometry-based approaches have a unique capacity to differentiate protein heterogeneity due to the ability to discriminate populations, whether minor or major, featuring modifications or complexation with non-covalent ligands on the basis of m/z. Cleavage of the peptide backbone can be further utilized to obtain residue-specific structural information. Here, hydrogen elimination monitoring (HEM) upon ultraviolet photodissociation (UVPD) of proteins transferred to the gas phase via nativespray ionization is introduced as an innovative approach to deduce backbone hydrogen bonding patterns. Using well-characterized peptides and a series of proteins, prediction of the engagement of the amide carbonyl oxygen of the protein backbone in hydrogen bonding using UVPD-HEM is demonstrated to show significant agreement with the hydrogen-bonding motifs derived from molecular dynamics simulations and X-ray crystal structures.
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31
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Daly S, MacAleese L, Dugourd P, Chirot F. Combining Structural Probes in the Gas Phase - Ion Mobility-Resolved Action-FRET. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2018; 29:133-139. [PMID: 29038996 DOI: 10.1007/s13361-017-1824-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Revised: 09/15/2017] [Accepted: 09/27/2017] [Indexed: 06/07/2023]
Abstract
In the context of native mass spectrometry, the development of gas-phase structural probes sensitive to the different levels of structuration of biomolecular assemblies is necessary to push forward conformational studies. In this paper, we provide the first example of the combination of ion mobility (IM) and Förster resonance energy transfer (FRET) measurements within the same experimental setup. The possibility to obtain mass- and mobility-resolved FRET measurements is demonstrated on a model peptide and applied to monitor the collision-induced unfolding of ubiquitin. Graphical Abstract ᅟ.
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Affiliation(s)
- Steven Daly
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière UMR 5306, F-69100, Villeurbanne, France
- Université de Bordeaux, INSERM U1212, CNRS UMR 5320, ARNA Laboratory, IECB, F-33600, Pessac, France
| | - Luke MacAleese
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière UMR 5306, F-69100, Villeurbanne, France
| | - Philippe Dugourd
- Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière UMR 5306, F-69100, Villeurbanne, France
| | - Fabien Chirot
- Univ Lyon, Université Claude Bernard Lyon 1, Ens de Lyon, CNRS, Institut des Sciences Analytiques UMR 5280, 5 rue de la Doua, F-69100, Villeurbanne, France.
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32
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Wagner ND, Clemmer DE, Russell DH. ESI-IM-MS and Collision-Induced Unfolding That Provide Insight into the Linkage-Dependent Interfacial Interactions of Covalently Linked Diubiquitin. Anal Chem 2017; 89:10094-10103. [DOI: 10.1021/acs.analchem.7b02932] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Nicole D. Wagner
- 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
| | - David H. Russell
- Department of Chemistry, Texas A&M University, College Station, Texas 77843, United States
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33
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Ghassabi Kondalaji S, Khakinejad M, Tafreshian A, J Valentine S. Comprehensive Peptide Ion Structure Studies Using Ion Mobility Techniques: Part 1. An Advanced Protocol for Molecular Dynamics Simulations and Collision Cross-Section Calculation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2017; 28:947-959. [PMID: 28211014 PMCID: PMC5942881 DOI: 10.1007/s13361-017-1599-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 01/07/2017] [Accepted: 01/09/2017] [Indexed: 05/02/2023]
Abstract
Collision cross-section (CCS) measurements with a linear drift tube have been utilized to study the gas-phase conformers of a model peptide (acetyl-PAAAAKAAAAKAAAAKAAAAK). Extensive molecular dynamics (MD) simulations have been conducted to derive an advanced protocol for the generation of a comprehensive pool of in-silico structures; both higher energy and more thermodynamically stable structures are included to provide an unbiased sampling of conformational space. MD simulations at 300 K are applied to the in-silico structures to more accurately describe the gas-phase transport properties of the ion conformers including their dynamics. Different methods used previously for trajectory method (TM) CCS calculation employing the Mobcal software [1] are evaluated. A new method for accurate CCS calculation is proposed based on clustering and data mining techniques. CCS values are calculated for all in-silico structures, and those with matching CCS values are chosen as candidate structures. With this approach, more than 300 candidate structures with significant structural variation are produced; although no final gas-phase structure is proposed here, in a second installment of this work, gas-phase hydrogen deuterium exchange data will be utilized as a second criterion to select among these structures as well as to propose relative populations for these ion conformers. Here the need to increase conformer diversity and accurate CCS calculation is demonstrated and the advanced methods are discussed. Graphical Abstract ᅟ.
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Affiliation(s)
| | - Mahdiar Khakinejad
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV, 26506, USA
| | - Amirmahdi Tafreshian
- Department of Statistics, West Virginia University, P.O. Box 6330, Morgantown, WV, 26506, USA
| | - Stephen J Valentine
- C. Eugene Bennett Department of Chemistry, West Virginia University, Morgantown, WV, 26506, USA.
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34
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Gillig KJ. Gas-phase protein conformation/multimer ion formation by electrospray ion mobility-mass spectrometry: bovine insulin and ubiquitin. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:20150368. [PMID: 27644980 PMCID: PMC5031634 DOI: 10.1098/rsta.2015.0368] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 07/28/2016] [Indexed: 06/06/2023]
Abstract
Ion mobility-mass spectrometry (IMMS) is a very attractive method for studies in structural biology because of the ability of rapid isolation by nearly simultaneous m/z characterization and size separation, leading to an emergence of IMMS as a complimentary biochemical tool. Earlier, we developed a method based on varying the protein concentration in solution prior to electrospray ionization (ESI) with subsequent m/z selection and dissociation of protein multimers by IMMS of cytochrome c. The focus of this work will be to correctly distinguish truly different ion conformations formed by ESI versus homomultimeric complexes with the same m/z for well-studied proteins bovine ubiquitin and insulin. These proteins were chosen due to their large difference in solution phase structures: insulin tightly bound by disulfide linkages, and ubiquitin-a protein that may adopt a range of states from compact to extended. Our preliminary results, as with cytochrome c reveal false negatives for protein oligomer formation and false positives for protein conformational states. In addition, these results will be couched in terms of the need for quantification of IMMS analysis of proteins given the total area under IMMS peaks can also distinguish conformation versus aggregation as higher order oligomers have more mass per ion.This article is part of the themed issue 'Quantitative mass spectrometry'.
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Affiliation(s)
- Kent J Gillig
- Genomics Research Center, Academia Sinica, 128 Academia Road, Nangang Section 2, Taipei 115, Taiwan, Republic of China
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35
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Garabedian A, Butcher D, Lippens JL, Miksovska J, Chapagain PP, Fabris D, Ridgeway ME, Park MA, Fernandez-Lima F. Structures of the kinetically trapped i-motif DNA intermediates. Phys Chem Chem Phys 2016; 18:26691-26702. [PMID: 27711445 PMCID: PMC5652045 DOI: 10.1039/c6cp04418b] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
In the present work, the conformational dynamics and folding pathways of i-motif DNA were studied in solution and in the gas-phase as a function of the solution pH conditions using circular dichroism (CD), photoacoustic calorimetry analysis (PAC), trapped ion mobility spectrometry-mass spectrometry (TIMS-MS), and molecular dynamics (MD). Solution studies showed at thermodynamic equilibrium the existence of a two-state folding mechanism, whereas during the pH = 7.0 → 4.5 transition a fast and slow phase (ΔHfast + ΔHslow = 43 ± 7 kcal mol-1) with a volume change associated with the formation of hemiprotonated cytosine base pairs and concomitant collapse of the i-motif oligonucleotide into a compact conformation were observed. TIMS-MS experiments showed that gas-phase, kinetically trapped i-motif DNA intermediates produced by nanoESI are preserved, with relative abundances depending on the solution pH conditions. In particular, a folded i-motif DNA structure was observed in nanoESI-TIMS-MS for low charge states in both positive and negative ion mode (e.g., z = ±3 to ±5) at low pH conditions. As solution pH increases, the cytosine neutralization leads to the loss of cytosine-cytosine+ (C·CH+) base pairing in the CCC strands and in those conditions we observe partially unfolded i-motif DNA conformations in nanoESI-TIMS-MS for higher charge states (e.g., z = -6 to -9). Collisional induced activation prior to TIMS-MS showed the existence of multiple local free energy minima, associated with the i-motif DNA unfolding at z = -6 charge state. For the first time, candidate gas-phase structures are proposed based on mobility measurements of the i-motif DNA unfolding pathway. Moreover, the inspection of partially unfolded i-motif DNA structures (z = -7 and z = -8 charge states) showed that the presence of inner cations may or may not induce conformational changes in the gas-phase. For example, incorporation of ammonium adducts does not lead to major conformational changes while sodium adducts may lead to the formation of sodium mediated bonds between two negatively charged sides inducing the stabilization towards more compact structures in new local, free energy minima in the gas-phase.
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Affiliation(s)
- Alyssa Garabedian
- Department of Chemistry and Biochemistry, Florida International University, Miami, USA.
| | - David Butcher
- Department of Chemistry and Biochemistry, Florida International University, Miami, USA.
| | | | - Jaroslava Miksovska
- Department of Chemistry and Biochemistry, Florida International University, Miami, USA. and Biomolecular Science Institute, Florida International University, Miami, USA
| | - Prem P Chapagain
- Biomolecular Science Institute, Florida International University, Miami, USA and Department of Physics, Florida International University, Miami, USA
| | | | | | - Melvin A Park
- Bruker Daltonics Inc., Billerica, Massachusetts, USA
| | - Francisco Fernandez-Lima
- Department of Chemistry and Biochemistry, Florida International University, Miami, USA. and Biomolecular Science Institute, Florida International University, Miami, USA
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36
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Benigni P, Fernandez-Lima F. Oversampling Selective Accumulation Trapped Ion Mobility Spectrometry Coupled to FT-ICR MS: Fundamentals and Applications. Anal Chem 2016; 88:7404-12. [DOI: 10.1021/acs.analchem.6b01946] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Paolo Benigni
- Department of Chemistry and Biochemistry and ‡Biomolecular Sciences
Institute, Florida International University, Miami, Florida 33199, United States
| | - Francisco Fernandez-Lima
- Department of Chemistry and Biochemistry and ‡Biomolecular Sciences
Institute, Florida International University, Miami, Florida 33199, United States
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37
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Ewing MA, Glover MS, Clemmer DE. Hybrid ion mobility and mass spectrometry as a separation tool. J Chromatogr A 2016; 1439:3-25. [DOI: 10.1016/j.chroma.2015.10.080] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 10/05/2015] [Accepted: 10/21/2015] [Indexed: 11/29/2022]
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38
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Larriba-Andaluz C, Fernández-García J, Ewing MA, Hogan CJ, Clemmer DE. Gas molecule scattering & ion mobility measurements for organic macro-ions in He versus N2 environments. Phys Chem Chem Phys 2016; 17:15019-29. [PMID: 25988389 DOI: 10.1039/c5cp01017a] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
A pending issue in linking ion mobility measurements to ion structures is that the collisional cross section (CCS, the measured structural parameter in ion mobility spectrometry) of an ion is strongly dependent upon the manner in which gas molecules effectively impinge on and are reemitted from ion surfaces (when modeling ions as fixed structures). To directly examine the gas molecule impingement and reemission processes and their influence, we measured the CCSs of positively charged ions of room temperature ionic liquids 1-ethyl-3-methylimidazolium dicyanamide (EMIM-N(CN)2) and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIM-BF4) in N2 using a differential mobility analyzer-mass spectrometer (DMA-MS) and in He using a drift tube mobility spectrometer-mass spectrometer (DT-MS). Cluster ions, generated via electrosprays, took the form (AB)N(A)z, spanning up to z = 20 and with masses greater than 100 kDa. As confirmed by molecular dynamics simulations, at the measurement temperature (∼300 K), such cluster ions took on globular conformations in the gas phase. Based upon their attained charge levels, in neither He nor N2 did the ion-induced dipole potential significantly influence gas molecule-ion collisions. Therefore, differences in the CCSs measured for ions in the two different gases could be primarily attributed to differences in gas molecule behavior upon collision with ions. Overwhelmingly, by comparison of predicted CCSs with selected input impingement-reemission laws to measurements, we find that in N2, gas molecules collide with ions diffusely--they are reemitted at random angles relative to the gas molecule incoming angle--and inelastically. Meanwhile, in He, gas molecules collide specularly and elastically and are emitted from ion surfaces at determined angles. The results can be rationalized on the basis of the momentum transferred per collision; in the case of He, individual gas molecule collisions minimally perturb the atoms within a cluster ion (internal motion), while in the case of N2, individual gas molecules have sufficiently large momentum to alter the internal motion in organic ions.
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Affiliation(s)
- Carlos Larriba-Andaluz
- University of Minnesota, Mechanical Engineering Department, 111 Church st. RM 2101A, Minneapolis, MN 55455, USA.
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39
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Morrison LJ, Brodbelt JS. Charge site assignment in native proteins by ultraviolet photodissociation (UVPD) mass spectrometry. Analyst 2016; 141:166-76. [PMID: 26596460 PMCID: PMC4679510 DOI: 10.1039/c5an01819f] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Characterization of all gas-phase charge sites of natively sprayed proteins and peptides is demonstrated using 193 nm UVPD. The high sequence coverage offered by UVPD is exploited for the accurate determination of charge sites in protein systems up to 18 kDa, allowing charge site to be studied as a function of protein conformation and the presence of disulfide bonds. Charging protons are found on both basic sidechains and on the amide backbone of less basic amino acids such as serine, glutamine, and proline. UVPD analysis was performed on the 3+ charge state of melittin, the 5+ to 8+ charge states of ubiquitin, and the 8+ charge state of reduced and oxidized β-lactoglobulin. The location of charges in gas-phase proteins is known to impact structure; molecular modeling of different charge site motifs of 3+ melittin demonstrates how placement of protons in simulations can dramatically impact the predicted structure of the molecule. The location of positive charge sites in ubiquitin and β-lactoglobulin are additionally found to depend on the presence or absence of salt-bridges, columbic repulsion across the length of the peptide, and protein conformation. Charge site isomers are demonstrated for ubiquitin and β-lactoglobulin but found to be much less numerous than previously predicted.
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40
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Servage KA, Silveira JA, Fort KL, Clemmer DE, Russell DH. Water-Mediated Dimerization of Ubiquitin Ions Captured by Cryogenic Ion Mobility-Mass Spectrometry. J Phys Chem Lett 2015; 6:4947-4951. [PMID: 26625010 DOI: 10.1021/acs.jpclett.5b02382] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The dynamics, structures, and functions of most biological molecules are strongly influenced by the nature of the peptide's or protein's interaction with water. Here, cryogenic ion mobility-mass spectrometry studies of ubiquitin have directly captured a water-mediated protein-protein binding event involving hydrated, noncovalently bound dimer ions in solution, and this interaction has potential relevance to one of the most important protein-protein interactions in nature. As solvent is removed, dimer ions, viz. [2 M + 14H](14+), can be stabilized by only a few attached water molecules prior to dissociation into individual monomeric ions. The hydrophobic patch of ubiquitin formed by the side chains of Leu-8, Ile-44, and Val-70 meet all the necessary conditions for a protein-protein binding "hot spot," including the requirement for occlusion of water to nearby hydrophilic sites, and it is suggested that this interaction is responsible for formation of the hydrated noncovalent ubiquitin dimer.
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Affiliation(s)
- Kelly A Servage
- Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States
| | - Joshua A Silveira
- Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States
| | - Kyle L Fort
- 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
| | - David H Russell
- Department of Chemistry, Texas A&M University , College Station, Texas 77843, United States
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41
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Nyon MP, Prentice T, Day J, Kirkpatrick J, Sivalingam GN, Levy G, Haq I, Irving JA, Lomas DA, Christodoulou J, Gooptu B, Thalassinos K. An integrative approach combining ion mobility mass spectrometry, X-ray crystallography, and nuclear magnetic resonance spectroscopy to study the conformational dynamics of α1 -antitrypsin upon ligand binding. Protein Sci 2015; 24:1301-12. [PMID: 26011795 PMCID: PMC4534181 DOI: 10.1002/pro.2706] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Revised: 05/05/2015] [Accepted: 05/11/2015] [Indexed: 11/11/2022]
Abstract
Native mass spectrometry (MS) methods permit the study of multiple protein species within solution equilibria, whereas ion mobility (IM)-MS can report on conformational behavior of specific states. We used IM-MS to study a conformationally labile protein (α1 -antitrypsin) that undergoes pathological polymerization in the context of point mutations. The folded, native state of the Z-variant remains highly polymerogenic in physiological conditions despite only minor thermodynamic destabilization relative to the wild-type variant. Various data implicate kinetic instability (conformational lability within a native state ensemble) as the basis of Z α1 -antitrypsin polymerogenicity. We show the ability of IM-MS to track such disease-relevant conformational behavior in detail by studying the effects of peptide binding on α1 -antitrypsin conformation and dynamics. IM-MS is, therefore, an ideal platform for the screening of compounds that result in therapeutically beneficial kinetic stabilization of native α1 -antitrypsin. Our findings are confirmed with high-resolution X-ray crystallographic and nuclear magnetic resonance spectroscopic studies of the same event, which together dissect structural changes from dynamic effects caused by peptide binding at a residue-specific level. IM-MS methods, therefore, have great potential for further study of biologically relevant thermodynamic and kinetic instability of proteins and provide rapid and multidimensional characterization of ligand interactions of therapeutic interest.
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Affiliation(s)
- Mun Peak Nyon
- Institute of Structural and Molecular Biology, Division of Biosciences, Division of Biosciences, University College London, London, WC1E 6BT, United Kingdom
| | - Tanya Prentice
- Institute of Structural and Molecular Biology, Division of Biosciences, Division of Biosciences, University College London, London, WC1E 6BT, United Kingdom
| | - Jemma Day
- Institute of Structural and Molecular Biology, Division of Biosciences, Division of Biosciences, University College London, London, WC1E 6BT, United Kingdom
| | - John Kirkpatrick
- Institute of Structural and Molecular Biology, Division of Biosciences, Division of Biosciences, University College London, London, WC1E 6BT, United Kingdom
| | - Ganesh N Sivalingam
- Institute of Structural and Molecular Biology, Division of Biosciences, Division of Biosciences, University College London, London, WC1E 6BT, United Kingdom
| | - Geraldine Levy
- Institute of Structural and Molecular Biology, Division of Biosciences, Division of Biosciences, University College London, London, WC1E 6BT, United Kingdom
| | - Imran Haq
- Wolfson Institute for Biomedical Research, Division of Medicine, University College London, London, WC1E 6BT, United Kingdom
| | - James A Irving
- Wolfson Institute for Biomedical Research, Division of Medicine, University College London, London, WC1E 6BT, United Kingdom
| | - David A Lomas
- Wolfson Institute for Biomedical Research, Division of Medicine, University College London, London, WC1E 6BT, United Kingdom
| | - John Christodoulou
- Institute of Structural and Molecular Biology, Division of Biosciences, Division of Biosciences, University College London, London, WC1E 6BT, United Kingdom.,Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, University of London, London, WC1E 7HX, United Kingdom
| | - Bibek Gooptu
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, University of London, London, WC1E 7HX, United Kingdom.,Division of Asthma, Allergy and Lung Biology, King's College London, Guy's Hospital, London, SE1 9RT, United Kingdom
| | - Konstantinos Thalassinos
- Institute of Structural and Molecular Biology, Division of Biosciences, Division of Biosciences, University College London, London, WC1E 6BT, United Kingdom.,Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, University of London, London, WC1E 7HX, United Kingdom
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42
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Warnke S, von Helden G, Pagel K. Analyzing the higher order structure of proteins with conformer-selective ultraviolet photodissociation. Proteomics 2015; 15:2804-12. [PMID: 25644066 DOI: 10.1002/pmic.201400480] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2014] [Revised: 12/19/2014] [Accepted: 01/28/2015] [Indexed: 11/09/2022]
Abstract
The top-down approach in protein sequencing requires simple methods in which the analyte can be readily dissociated at every position along the backbone. In this context, ultraviolet photodissociation (UVPD) recently emerged as a promising tool because, in contrast to slow heating techniques such as CID, the absorption of UV light is followed by a rather statistically distributed cleavage of backbone bonds. As a result, nearly complete sequence coverage can be obtained. It is well known, however, that gas-phase proteins can adopt a variety of different, sometimes coexisting conformations and the influence of this structural diversity on the UVPD fragmentation behavior is not clear. Using ion mobility-UVPD-MS, we recently showed that UVPD is sensitive to the higher order structure of gas-phase proteins. In particular, the cis/trans isomerization of certain proline peptide bonds was shown to significantly influence the UVPD fragmentation pattern of two extended conformers of 11(+) ubiquitin. Building on these results, we here provide conformer-selective UVPD data for 7(+) ubiquitin ions, which are known to be present in a much more diverse and wider ensemble of different structures, ranging from very compact to highly extended species. Our data show that certain conformers fall into groups with similar UVPD fragmentation pattern. Surprisingly, however, the conformers within each group can differ tremendously in their collision cross-section. This indicates that the multiple coexisting conformations typically observed for 7(+) ubiquitin are caused by a few, not easily interconvertible, subpopulations.
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Affiliation(s)
- Stephan Warnke
- Fritz Haber Institute of the Max Planck Society, Berlin, Germany
| | - Gert von Helden
- Fritz Haber Institute of the Max Planck Society, Berlin, Germany
| | - Kevin Pagel
- Fritz Haber Institute of the Max Planck Society, Berlin, Germany.,Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin, Germany
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43
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Schenk ER, Almeida R, Miksovska J, Ridgeway ME, Park MA, Fernandez-Lima F. Kinetic intermediates of holo- and apo-myoglobin studied using HDX-TIMS-MS and molecular dynamic simulations. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2015; 26:555-63. [PMID: 25690175 PMCID: PMC4402236 DOI: 10.1007/s13361-014-1067-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 12/01/2014] [Accepted: 12/07/2014] [Indexed: 05/05/2023]
Abstract
In the present work, the kinetic intermediates of holo- and apo-myoglobin were studied by correlating the ion-neutral collision cross section and time resolved H/D back exchange rate simultaneously in a trapped ion mobility spectrometer coupled to a mass spectrometer (HDX-TIMS-MS). The high mobility resolution of the TIMS cell permitted the observation of multiple IMS bands and complementary molecular dynamics simulations resulted in the assignment of candidate structures for each experimental condition studied (e.g., holo [M + 8H](+8)-[M + 9H](+9) and apo [M + 9H](+9)-[M + 19H](+19)). Inspection of the kinetic intermediates suggests that the tertiary structure of apomyoglobin unfolds quickly upon the loss of the Fe protoporphyrin IX that stabilizes the interactions between the A, G, and H helices. In the absence of the porphyrin heme, the apomyoglobin unfolds to Xn kinetic intermediates that vary in the extent of unfolding as a result of the observed charge state.
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Affiliation(s)
- Emily R. Schenk
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
- Biomolecular Sciences Institute, Florida International University, Miami, FL 33199, USA
| | - Raybel Almeida
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | - Jaroslava Miksovska
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
| | | | | | - Francisco Fernandez-Lima
- Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA
- Biomolecular Sciences Institute, Florida International University, Miami, FL 33199, USA
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44
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Ridgeway ME, Silveira JA, Meier JE, Park MA. Microheterogeneity within conformational states of ubiquitin revealed by high resolution trapped ion mobility spectrometry. Analyst 2015; 140:6964-72. [DOI: 10.1039/c5an00841g] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The present work employs trapped ion mobility spectrometry (TIMS) for the analysis of ubiquitin ions known to display a multitude of previously unresolved interchangeable conformations upon electrospray ionization.
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45
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Rajabi K. Microsecond pulsed hydrogen/deuterium exchange of electrosprayed ubiquitin ions stored in a linear ion trap. Phys Chem Chem Phys 2015; 17:3607-16. [DOI: 10.1039/c4cp04716h] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The pulsed HDX MS method is sampling a population of ubiquitin ions with a similar backbone fold as solution.
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Affiliation(s)
- Khadijeh Rajabi
- Department of Chemistry
- University of British Columbia (UBC)
- Vancouver
- Canada
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46
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Maurer MM, Donohoe GC, Valentine SJ. Advances in ion mobility-mass spectrometry instrumentation and techniques for characterizing structural heterogeneity. Analyst 2015; 140:6782-98. [PMID: 26114255 DOI: 10.1039/c5an00922g] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Enabling IM-MS instrumentation and techniques for characterizing sample structural heterogeneity have developed rapidly over the last five years.
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Affiliation(s)
- Megan M. Maurer
- C. Eugene Bennett Department of Chemistry
- West Virginia University
- Morgantown
- USA
| | - Gregory C. Donohoe
- C. Eugene Bennett Department of Chemistry
- West Virginia University
- Morgantown
- USA
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47
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Voronina L, Rizzo TR. Spectroscopic studies of kinetically trapped conformations in the gas phase: the case of triply protonated bradykinin. Phys Chem Chem Phys 2015; 17:25828-36. [DOI: 10.1039/c5cp01651g] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We explore conformational space of triply protonated bradykinin. Three conformational families are mobility-separated and spectroscopically characterized. Kinetically trapped structures are identified via annealing.
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Affiliation(s)
- Liudmila Voronina
- Laboratoire de Chimie Physique Moléculaire
- École Polytechnique Fédérale de Lausanne
- EPFL SB ISIC LCPM
- CH-1015 Lausanne
- Switzerland
| | - Thomas R. Rizzo
- Laboratoire de Chimie Physique Moléculaire
- École Polytechnique Fédérale de Lausanne
- EPFL SB ISIC LCPM
- CH-1015 Lausanne
- Switzerland
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48
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Shi H, Atlasevich N, Merenbloom SI, Clemmer DE. Solution dependence of the collisional activation of ubiquitin [M + 7H](7+) ions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:2000-8. [PMID: 24658799 PMCID: PMC4171273 DOI: 10.1007/s13361-014-0834-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 12/31/2013] [Accepted: 01/10/2014] [Indexed: 05/12/2023]
Abstract
The solution dependence of gas-phase unfolding for ubiquitin [M + 7H](7+) ions has been studied by ion mobility spectrometry-mass spectrometry (IMS-MS). Different acidic water:methanol solutions are used to favor the native (N), more helical (A), or unfolded (U) solution states of ubiquitin. Unfolding of gas-phase ubiquitin ions is achieved by collisional heating and newly formed structures are examined by IMS. With an activation voltage of 100 V, a selected distribution of compact structures unfolds, forming three resolvable elongated states (E1-E3). The relative populations of these elongated structures depend strongly on the solution composition. Activation of compact ions from aqueous solutions known to favor N-state ubiquitin produces mostly the E1 type elongated state, whereas activation of compact ions from methanol containing solutions that populate A-state ubiquitin favors the E3 elongated state. Presumably, this difference arises because of differences in precursor ion structures emerging from solution. Thus, it appears that information about solution populations can be retained after ionization, selection, and activation to produce the elongated states. These data as well as others are discussed.
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