1
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Jeon CK, Rojas Ramirez C, Makey DM, Kurulugama RT, Ruotolo BT. CIUSuite 3: Next-Generation CCS Calibration and Automated Data Analysis Tools for Gas-Phase Protein Unfolding Data. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2024. [PMID: 38967378 DOI: 10.1021/jasms.4c00176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/06/2024]
Abstract
Ion mobility-mass spectrometry (IM-MS) has become a technology deployed across a wide range of structural biology applications despite the challenges in characterizing closely related protein structures. Collision-induced unfolding (CIU) has emerged as a valuable technique for distinguishing closely related, iso-cross-sectional protein and protein complex ions through their distinct unfolding pathways in the gas phase. With the speed and sensitivity of CIU analyses, there has been a rapid growth of CIU-based assays, especially regarding biomolecular targets that remain challenging to assess and characterize with other structural biology tools. With information-rich CIU data, many software tools have been developed to automate laborious data analysis. However, with the recent development of new IM-MS technologies, such as cyclic IM-MS, CIU continues to evolve, necessitating improved data analysis tools to keep pace with new technologies and facilitating the automation of various data processing tasks. Here, we present CIUSuite 3, a software package that contains updated algorithms that support various IM-MS platforms and supports the automation of various data analysis tasks such as peak detection, multidimensional classification, and collision cross section (CCS) calibration. CIUSuite 3 uses local maxima searches along with peak width and prominence filters to detect peaks to automate CIU data extraction. To support both the primary CIU (CIU1) and secondary CIU (CIU2) experiments enabled by cyclic IM-MS, two-dimensional data preprocessing is deployed, which allows multidimensional classification. Our data suggest that additional dimensions in classification improve the overall accuracy of class assignments. CIUSuite 3 also supports CCS calibration for both traveling wave and drift tube IM-MS, and we demonstrate the accuracy of a new single-field CCS calibration method designed for drift tube IM-MS leveraging calibrant CIU data. Overall, CIUSuite 3 is positioned to support current and next-generation IM-MS and CIU assay development deployed in an automated format.
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Affiliation(s)
- Chae Kyung Jeon
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | | | - Devin M Makey
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | | | - Brandon T Ruotolo
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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2
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Jayasekera HS, Mohona FA, Ewbank M, Marty MT. Simultaneous Native Mass Spectrometry Analysis of Single and Double Mutants To Probe Lipid Binding to Membrane Proteins. Anal Chem 2024; 96:10426-10433. [PMID: 38859611 PMCID: PMC11215972 DOI: 10.1021/acs.analchem.4c01704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2024]
Abstract
Lipids are critical modulators of membrane protein structure and function. However, it is challenging to investigate the thermodynamics of protein-lipid interactions because lipids can simultaneously bind membrane proteins at different sites with different specificities. Here, we developed a native mass spectrometry (MS) approach using single and double mutants to measure the relative energetic contributions of specific residues on Aquaporin Z (AqpZ) toward cardiolipin (CL) binding. We first mutated potential lipid-binding residues on AqpZ, and mixed mutant and wild-type proteins together with CL. By using native MS to simultaneously resolve lipid binding to the mutant and wild-type proteins in a single spectrum, we directly determined the relative affinities of CL binding, thereby revealing the relative Gibbs free energy change for lipid binding caused by the mutation. Comparing different mutants revealed that W14 contributes to the tightest CL binding site, with R224 contributing to a lower affinity site. Using double mutant cycling, we investigated the synergy between W14 and R224 sites on CL binding. Overall, this novel native MS approach provides unique insights into the binding of lipids to specific sites on membrane proteins.
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Affiliation(s)
- Hiruni S. Jayasekera
- Department of Chemistry and Biochemistry and Bio5 Institute, University of Arizona, Tucson, Arizona 85721
| | - Farhana Afrin Mohona
- Department of Chemistry and Biochemistry and Bio5 Institute, University of Arizona, Tucson, Arizona 85721
| | - Megan Ewbank
- Department of Chemistry and Biochemistry and Bio5 Institute, University of Arizona, Tucson, Arizona 85721
| | - Michael T. Marty
- Department of Chemistry and Biochemistry and Bio5 Institute, University of Arizona, Tucson, Arizona 85721
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3
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Ju H, Cheng L, Li M, Mei K, He S, Jia C, Guo X. Single-Molecule Electrical Profiling of Peptides and Proteins. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024:e2401877. [PMID: 38639403 DOI: 10.1002/advs.202401877] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Revised: 04/03/2024] [Indexed: 04/20/2024]
Abstract
In recent decades, there has been a significant increase in the application of single-molecule electrical analysis platforms in studying proteins and peptides. These advanced analysis methods have the potential for deep investigation of enzymatic working mechanisms and accurate monitoring of dynamic changes in protein configurations, which are often challenging to achieve in ensemble measurements. In this work, the prominent research progress in peptide and protein-related studies are surveyed using electronic devices with single-molecule/single-event sensitivity, including single-molecule junctions, single-molecule field-effect transistors, and nanopores. In particular, the successful commercial application of nanopores in DNA sequencing has made it one of the most promising techniques in protein sequencing at the single-molecule level. From single peptides to protein complexes, the correlation between their electrical characteristics, structures, and biological functions is gradually being established. This enables to distinguish different molecular configurations of these biomacromolecules through real-time electrical monitoring of their life activities, significantly improving the understanding of the mechanisms underlying various life processes.
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Affiliation(s)
- Hongyu Ju
- School of Pharmaceutical Science and Technology, Tianjin University, Tianjin, 300072, P. R. China
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Microscale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, Tianjin, 300350, P. R. China
| | - Li Cheng
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Microscale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, Tianjin, 300350, P. R. China
| | - Mengmeng Li
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Microscale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, Tianjin, 300350, P. R. China
| | - Kunrong Mei
- School of Pharmaceutical Science and Technology, Tianjin University, Tianjin, 300072, P. R. China
| | - Suhang He
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Microscale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, Tianjin, 300350, P. R. China
| | - Chuancheng Jia
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Microscale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, Tianjin, 300350, P. R. China
| | - Xuefeng Guo
- Center of Single-Molecule Sciences, Institute of Modern Optics, Frontiers Science Center for New Organic Matter, Tianjin Key Laboratory of Microscale Optical Information Science and Technology, College of Electronic Information and Optical Engineering, Nankai University, Tianjin, 300350, P. R. China
- Beijing National Laboratory for Molecular Sciences, National Biomedical Imaging Center, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, P. R. China
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4
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Deslignière E, Yin VC, Ebberink EHTM, Rolland AD, Barendregt A, Wörner TP, Nagornov KO, Kozhinov AN, Fort KL, Tsybin YO, Makarov AA, Heck AJR. Ultralong transients enhance sensitivity and resolution in Orbitrap-based single-ion mass spectrometry. Nat Methods 2024; 21:619-622. [PMID: 38443506 DOI: 10.1038/s41592-024-02207-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2023] [Accepted: 02/07/2024] [Indexed: 03/07/2024]
Abstract
Orbitrap-based charge detection mass spectrometry utilizes single-molecule sensitivity to enable mass analysis of even highly heterogeneous, high-mass macromolecular assemblies. For contemporary Orbitrap instruments, the accessible ion detection (recording) times are maximally ~1-2 s. Here by modifying a data acquisition method on an Orbitrap ultrahigh mass range mass spectrometer, we trapped and monitored individual (single) ions for up to 25 s, resulting in a corresponding and huge improvement in signal-to-noise ratio (×5 compared with 1 s), mass resolution (×25) and accuracy in charge and mass determination of Orbitrap-based charge detection mass spectrometry.
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Affiliation(s)
- Evolène Deslignière
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands
| | - Victor C Yin
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands.
| | - Eduard H T M Ebberink
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands
| | - Amber D Rolland
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands
| | - Arjan Barendregt
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands
| | | | | | | | - Kyle L Fort
- Thermo Fisher Scientific (Bremen) GmbH, Bremen, Germany
| | | | - Alexander A Makarov
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands
- Thermo Fisher Scientific (Bremen) GmbH, Bremen, Germany
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Centre for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Utrecht, the Netherlands.
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5
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De los Santos L, Beckman RL, DeBarro C, Keener JE, Torres MD, de la Fuente-Nunez C, Brodbelt JS, Fleeman RM. Polyproline peptide targets Klebsiella pneumoniae polysaccharides to collapse biofilms. CELL REPORTS. PHYSICAL SCIENCE 2024; 5:101869. [PMID: 38605913 PMCID: PMC11008256 DOI: 10.1016/j.xcrp.2024.101869] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/13/2024]
Abstract
Hypervirulent Klebsiella pneumoniae is known for its increased extracellular polysaccharide production. Biofilm matrices of hypervirulent K. pneumoniae have increased polysaccharide abundance and are uniquely susceptible to disruption by peptide bactenecin 7 (bac7 (1-35)). Here, using confocal microscopy, we show that polysaccharides within the biofilm matrix collapse following bac7 (1-35) treatment. This collapse led to the release of cells from the biofilm, which were then killed by the peptide. Characterization of truncated peptide analogs revealed that their interactions with polysaccharide were responsible for the biofilm matrix changes that accompany bac7 (1-35) treatment. Ultraviolet photodissociation mass spectrometry with the parental peptide or a truncated analog bac7 (10-35) reveal the important regions for bac7 (1-35) complexing with polysaccharides. Finally, we tested bac7 (1-35) using a murine skin abscess model and observed a significant decrease in the bacterial burden. These findings unveil the potential of bac7 (1-35) polysaccharide interactions to collapse K. pneumoniae biofilms.
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Affiliation(s)
- Laura De los Santos
- Division of Immunity and Pathogenesis, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32827, USA
| | - Robert L. Beckman
- Division of Immunity and Pathogenesis, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32827, USA
| | - Christina DeBarro
- Division of Immunity and Pathogenesis, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32827, USA
| | - James E. Keener
- Department of Chemistry, The University of Texas at Austin, Austin, TX 78712, USA
| | - Marcelo D.T. Torres
- Machine Biology Group, Departments of Psychiatry and Microbiology, Institute for Biomedical Informatics, Institute for Translational Medicine and Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Departments of Bioengineering and Chemical and Biomolecular Engineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Chemistry, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA, USA
- Penn Institute for Computational Science, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Cesar de la Fuente-Nunez
- Machine Biology Group, Departments of Psychiatry and Microbiology, Institute for Biomedical Informatics, Institute for Translational Medicine and Therapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
- Departments of Bioengineering and Chemical and Biomolecular Engineering, School of Engineering and Applied Science, University of Pennsylvania, Philadelphia, PA 19104, USA
- Department of Chemistry, School of Arts and Sciences, University of Pennsylvania, Philadelphia, PA, USA
- Penn Institute for Computational Science, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jennifer S. Brodbelt
- Department of Chemistry, The University of Texas at Austin, Austin, TX 78712, USA
| | - Renee M. Fleeman
- Division of Immunity and Pathogenesis, Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32827, USA
- X (formerly Twitter): @FleemanLab
- Lead contact
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6
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Shepherd SO, Green AW, Resendiz ES, Newton KR, Kurulugama RT, Prell JS. Effects of Nano-Electrospray Ionization Emitter Position on Unintentional In-Source Activation of Peptide and Protein Ions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2024; 35:498-507. [PMID: 38374644 DOI: 10.1021/jasms.3c00371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/21/2024]
Abstract
Native ion mobility-mass spectrometry (IM-MS) typically introduces protein ions into the gas phase through nano-electrospray ionization (nESI). Many nESI setups have mobile stages for tuning the ion signal and extent of co-solute and salt adduction. However, tuning the position of the emitter capillary in nESI can have unintended downstream consequences for collision-induced unfolding or collision-induced dissociation (CIU/D) experiments. Here, we show that relatively small variations in the nESI emitter position can shift the midpoint (commonly called the "CID50" or "CIU50") potential of CID breakdown curves and CIU transitions by as much as 8 V on commercial instruments. A spatial "map" of the shift in CID50 for the loss of heme from holomyoglobin onto the emitter position on a Waters Synapt G2-Si mass spectrometer shows that emitter positions closer to the instrument inlet can result in significantly greater in-source activation, whereas different effects are found on an Agilent 6545XT instrument for the ions studied. A similar effect is observed for CID of the singly protonated leucine enkephalin peptide and Shiga toxin 1 subunit B homopentamer on the Waters Synapt G2-Si instrument. In-source activation effects on a Waters Synapt G2-Si are also investigated by examining the RMSD between CIU fingerprints acquired at different emitter positions and the shifts in CIU50 for structural transitions of bovine serum albumin and NIST monoclonal antibody.
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Affiliation(s)
- Samantha O Shepherd
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1253, United States
| | - Austin W Green
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1253, United States
| | - Elizabeth S Resendiz
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1253, United States
| | - Kenneth R Newton
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1253, United States
- Agilent Technologies, 5301 Stevens Creek Blvd, Santa Clara, California 95051, United States
| | - Ruwan T Kurulugama
- Agilent Technologies, 5301 Stevens Creek Blvd, Santa Clara, California 95051, United States
| | - James S Prell
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403-1253, United States
- Materials Science Institute, University of Oregon, Eugene, Oregon 97403-1252, United States
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7
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Parikh RA, Draper BE, Jarrold MF. Multiple Ion Charge Extraction (MICE) for High-Throughput Charge Detection Mass Spectrometry. Anal Chem 2024. [PMID: 38329825 DOI: 10.1021/acs.analchem.3c05087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/10/2024]
Abstract
Charge detection mass spectrometry (CD-MS) is a single-particle technique, where the masses of individual ions are determined from simultaneous measurements of their mass-to-charge ratio (m/z) and charge. The ions are trapped in an electrostatic linear ion trap (ELIT) and oscillate back and forth through a conducting cylinder connected to a charge-sensitive amplifier. The oscillating ions generate a periodic signal that is processed with fast Fourier transforms (FFTs) to obtain the oscillation frequency (which is related to m/z) and magnitude (which is proportional to the charge). The simultaneous trapping of two or more ions is a way to increase throughput. However, when multiple ions are trapped, it is possible that some of them have overlapping oscillation frequencies, which can lead to an error in the charge determination. To avoid this error, results from overlapping ions are usually discarded. When measurements are performed with many trapped ions, the most abundant m/z species are discarded at a higher rate, which affects the relative abundances in the mass distribution. Here, we report the development of a post-processing method called multiple ion charge extraction (MICE) that uses a statistical approach to assign charges to ions with overlapping frequencies. MICE recovers single-ion information from high signal measurements and makes the relative abundances more resilient to the signal intensity. This approach corrects for high signal m/z biasing, allowing analysis to be faster and more reliable. Using MICE, CD-MS measurements were made at rates of 120 ions/s with little m/z biasing.
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Affiliation(s)
- Raj A Parikh
- Chemistry Department, Indiana University, 800 E Kirkwood Ave, Bloomington, Indiana 47405, United States
| | - Benjamin E Draper
- Megadalton Solutions Inc., 3750 E Bluebird Ln, Bloomington, Indiana 47401, United States
| | - Martin F Jarrold
- Chemistry Department, Indiana University, 800 E Kirkwood Ave, Bloomington, Indiana 47405, United States
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8
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van Wonderen JH, Crack JC, Edwards MJ, Clarke TA, Saalbach G, Martins C, Butt JN. Liquid-chromatography mass spectrometry describes post-translational modification of Shewanella outer membrane proteins. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184221. [PMID: 37673350 DOI: 10.1016/j.bbamem.2023.184221] [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] [Received: 02/08/2023] [Revised: 08/09/2023] [Accepted: 08/30/2023] [Indexed: 09/08/2023]
Abstract
Electrogenic bacteria deliver excess respiratory electrons to externally located metal oxide particles and electrodes. The biochemical basis for this process is arguably best understood for species of Shewanella where the integral membrane complex termed MtrCAB is key to electron transfer across the bacterial outer membranes. A crystal structure was recently resolved for MtrCAB from S. baltica OS185. However, X-ray diffraction did not resolve the N-terminal residues so that the lipidation status of proteins in the mature complex was poorly described. Here we report liquid chromatography mass spectrometry revealing the intact mass values for all three proteins in the MtrCAB complexes purified from Shewanella oneidensis MR-1 and S. baltica OS185. The masses of MtrA and MtrB are consistent with both proteins being processed by Signal Peptidase I and covalent attachment of ten c-type hemes to MtrA. The mass of MtrC is most reasonably interpreted as arising from protein processed by Signal Peptidase II to produce a diacylated lipoprotein containing ten c-type hemes. Our two-step protocol for liquid-chromatography mass spectrometry used a reverse phase column to achieve on-column detergent removal prior to gradient protein resolution and elution. We envisage the method will be capable of simultaneously resolving the intact mass values for multiple proteins in other membrane protein complexes.
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Affiliation(s)
- Jessica H van Wonderen
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
| | - Jason C Crack
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Marcus J Edwards
- School of Biological Sciences, University of East Anglia, , Norwich Research Park, Norwich NR4 7TJ, UK; School of Life Sciences, University of Essex, Colchester CO4 3SQ, UK
| | - Thomas A Clarke
- School of Biological Sciences, University of East Anglia, , Norwich Research Park, Norwich NR4 7TJ, UK
| | - Gerhard Saalbach
- Proteomics Facility, The John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
| | - Carlo Martins
- Proteomics Facility, The John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
| | - Julea N Butt
- School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK; School of Biological Sciences, University of East Anglia, , Norwich Research Park, Norwich NR4 7TJ, UK.
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9
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Jayasekera HS, Mohona FA, Ewbank M, Marty MT. SIMULTANEOUS NATIVE MASS SPECTROMETRY ANALYSIS OF SINGLE AND DOUBLE MUTANTS TO PROBE LIPID BINDING TO MEMBRANE PROTEINS. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.19.558516. [PMID: 37781586 PMCID: PMC10541089 DOI: 10.1101/2023.09.19.558516] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/03/2023]
Abstract
Lipids are critical modulators of membrane protein structure and function. However, it is challenging to investigate the thermodynamics of protein-lipid interactions because lipids can simultaneously bind membrane proteins at different sites with different specificities. Here, we developed a native mass spectrometry (MS) approach using single and double mutants to measure the relative energetic contributions of specific residues on Aquaporin Z (AqpZ) toward cardiolipin (CL) binding. We first mutated potential lipid-binding residues on AqpZ, and mixed mutant and wild-type proteins together with CL. By using native MS to simultaneously resolve lipid binding to the mutant and wild-type proteins in a single spectrum, we directly determined the relative affinities of CL binding, thereby revealing the relative Gibbs free energy change for lipid binding caused by the mutation. Comparing different mutants revealed that the W14 contributes to the tightest CL binding site, with R224 contributing to a lower affinity site. Using double mutant cycling, we investigated the synergy between W14 and R224 sites on CL binding. Overall, this novel native MS approach provides unique insights into lipid binding to specific sites on membrane proteins.
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Affiliation(s)
- Hiruni S. Jayasekera
- [a] Department of Chemistry and Biochemistry and Bio5 Institute, University of Arizona, Tucson, AZ 85721
| | - Farhana Afrin Mohona
- [a] Department of Chemistry and Biochemistry and Bio5 Institute, University of Arizona, Tucson, AZ 85721
| | - Megan Ewbank
- [a] Department of Chemistry and Biochemistry and Bio5 Institute, University of Arizona, Tucson, AZ 85721
| | - Michael T. Marty
- [a] Department of Chemistry and Biochemistry and Bio5 Institute, University of Arizona, Tucson, AZ 85721
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10
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Levesque I, Juliano BR, Parson KF, Ruotolo BT. A Critical Evaluation of Detergent Exchange Methodologies for Membrane Protein Native Mass Spectrometry. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:2662-2671. [PMID: 37956121 DOI: 10.1021/jasms.3c00230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
Membrane proteins (MPs) play many critical roles in cellular physiology and constitute the majority of current pharmaceutical targets. However, MPs are comparatively understudied relative to soluble proteins due to the challenges associated with their solubilization in membrane mimetics. Native mass spectrometry (nMS) has emerged as a useful technique to probe the structures of MPs. Typically, nMS studies using MPs have employed detergent micelles to solubilize the MP. Oftentimes, the detergent micelle that the MP was purified in will be exchanged into another detergent prior to analysis by nMS. While methodologies for performing detergent exchange have been extensively described in prior reports, the effectiveness of these protocols remains understudied. Here, we present a critical analysis of detergent exchange efficacy using several model transmembrane proteins and a variety of commonly used detergents, evaluating the completeness of the exchange using a battery of existing protocols. Our data include results for octyl glucoside (OG), octaethylene glycol monododecyl ether (C12E8), and tetraethylene glycol monooctyl ether (C8E4), and these data demonstrate that existing protocols are insufficient and yield incomplete exchange for the proteins under the conditions probed here. In some cases, our data indicate that up to 99% of the measured detergent corresponds to the original pre-exchange detergent rather than the desired post-exchange detergent. We conclude by discussing the need for new detergent exchange methodologies alongside improved exchange yield expectations for studying the potential influence of detergents on MP structures.
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Affiliation(s)
- Iliana Levesque
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Brock R Juliano
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Kristine F Parson
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Brandon T Ruotolo
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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11
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Talbot FO, Suarez CM, Nagy AM, Chen JC, Djavani-Tabrizi I, Clotea I, Jockusch RA. Robust Fluorescence Collection Module for Wide-Bore Ion Cyclotron Resonance Mass Spectrometers. Anal Chem 2023; 95:17193-17202. [PMID: 37963234 DOI: 10.1021/acs.analchem.3c01801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2023]
Abstract
Mass spectrometers are at the heart of the most powerful toolboxes available to scientists when studying molecular structure, conformation, and dynamics in controlled molecular environments. Improved molecular characterization brought about by the implementation of new orthogonal methods into mass spectrometry-enabled analyses opens deeper insight into the complex interplay of forces that underlie chemistry. Here, we detail how one can add fluorescence detection to commercial ultrahigh-resolution Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometers without adverse effects to its preexisting analytical tools. This advance enables measurements based on fluorescence detection, such as Förster resonance energy transfer (FRET), to be used in conjunction with other MS/MS techniques to probe the conformation and dynamics of large biomolecules, such as proteins and their complexes, in the highly controlled environment of a Penning trap.
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Affiliation(s)
- Francis O Talbot
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Cynthia M Suarez
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Andrea M Nagy
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - JoAnn C Chen
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Iden Djavani-Tabrizi
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Ioana Clotea
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
| | - Rebecca A Jockusch
- Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
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12
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Konermann L, Liu Z, Haidar Y, Willans MJ, Bainbridge NA. On the Chemistry of Aqueous Ammonium Acetate Droplets during Native Electrospray Ionization Mass Spectrometry. Anal Chem 2023; 95:13957-13966. [PMID: 37669319 DOI: 10.1021/acs.analchem.3c02546] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/07/2023]
Abstract
Ammonium acetate (NH4Ac) is a widely used solvent additive in native electrospray ionization (ESI) mass spectrometry. NH4Ac can undergo proton transfer to form ammonia and acetic acid (NH4+ + Ac- → NH3 + HAc). The volatility of these products ensures that electrosprayed ions are free of undesired adducts. NH4Ac dissolution in water yields pH 7, providing "physiological" conditions. However, NH4Ac is not a buffer at pH 7 because NH4+ and Ac- are not a conjugate acid/base pair (Konermann, L. J. Am. Soc. Mass Spectrom. 2017, 28, 1827-1835.). In native ESI, it is desirable that analytes experience physiological conditions not only in bulk solution but also while they reside in ESI droplets. Little is known about the internal milieu of NH4Ac-containing ESI droplets. The current work explored the acid/base chemistry of such droplets, starting from a pH 7 analyte solution. We used a two-pronged approach involving evaporation experiments on bulk solutions under ESI-mimicking conditions, as well as molecular dynamics simulations using a newly developed algorithm that allows for proton transfer. Our results reveal that during droplet formation at the tip of the Taylor cone, electrolytically generated protons get neutralized by Ac-, making NH4+ the net charge carriers in the weakly acidic nascent droplets. During the subsequent evaporation, the droplets lose water as well as NH3 and HAc that were generated by proton transfer. NH3 departs more quickly because of its greater volatility, causing the accumulation of HAc. Together with residual Ac-, these HAc molecules form an acetate buffer that stabilizes the average droplet pH at 5.4 ± 0.1, as governed by the Henderson-Hasselbalch equation. The remarkable success of native ESI investigations in the literature implies that this pH drop by ∼1.6 units relative to the initially neutral analyte solution can be tolerated by most biomolecular analytes on the short time scale of the ESI process.
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Affiliation(s)
- Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Zeyuan Liu
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Yousef Haidar
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Mathew J Willans
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Nicholas A Bainbridge
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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13
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Lutomski CA, El‐Baba TJ, Hinkle JD, Liko I, Bennett JL, Kalmankar NV, Dolan A, Kirschbaum C, Greis K, Urner LH, Kapoor P, Yen H, Pagel K, Mullen C, Syka JEP, Robinson CV. Infrared Multiphoton Dissociation Enables Top-Down Characterization of Membrane Protein Complexes and G Protein-Coupled Receptors. Angew Chem Int Ed Engl 2023; 62:e202305694. [PMID: 37329506 PMCID: PMC7615181 DOI: 10.1002/anie.202305694] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Revised: 05/20/2023] [Accepted: 06/15/2023] [Indexed: 06/19/2023]
Abstract
Membrane proteins are challenging to analyze by native mass spectrometry (MS) as their hydrophobic nature typically requires stabilization in detergent micelles that are removed prior to analysis via collisional activation. There is however a practical limit to the amount of energy which can be applied, which often precludes subsequent characterization by top-down MS. To overcome this barrier, we have applied a modified Orbitrap Eclipse Tribrid mass spectrometer coupled to an infrared laser within a high-pressure linear ion trap. We show how tuning the intensity and time of incident photons enables liberation of membrane proteins from detergent micelles. Specifically, we relate the ease of micelle removal to the infrared absorption of detergents in both condensed and gas phases. Top-down MS via infrared multiphoton dissociation (IRMPD), results in good sequence coverage enabling unambiguous identification of membrane proteins and their complexes. By contrasting and comparing the fragmentation patterns of the ammonia channel with two class A GPCRs, we identify successive cleavage of adjacent amino acids within transmembrane domains. Using gas-phase molecular dynamics simulations, we show that areas prone to fragmentation maintain aspects of protein structure at increasing temperatures. Altogether, we propose a rationale to explain why and where in the protein fragment ions are generated.
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Affiliation(s)
- Corinne A. Lutomski
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Tarick J. El‐Baba
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | | | | | - Jack L. Bennett
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Neha V. Kalmankar
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Andrew Dolan
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Carla Kirschbaum
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
| | - Kim Greis
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
| | - Leonhard H. Urner
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
- Department of Chemistry and Chemical BiologyTU Dortmund UniversityDortmund44227Germany
| | | | - Hsin‐Yung Yen
- OMass TherapeuticsOxfordOX4 2GXUK
- Institute of Biological ChemistryAcademia SinicaTaipei115Taiwan
| | - Kevin Pagel
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
| | | | | | - Carol V. Robinson
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
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14
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Lutomski CA, El‐Baba TJ, Hinkle JD, Liko I, Bennett JL, Kalmankar NV, Dolan A, Kirschbaum C, Greis K, Urner LH, Kapoor P, Yen H, Pagel K, Mullen C, Syka JEP, Robinson CV. Infrared Multiphoton Dissociation Enables Top-Down Characterization of Membrane Protein Complexes and G Protein-Coupled Receptors. ANGEWANDTE CHEMIE (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 135:e202305694. [PMID: 38516403 PMCID: PMC10953453 DOI: 10.1002/ange.202305694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/24/2023] [Indexed: 03/23/2024]
Abstract
Membrane proteins are challenging to analyze by native mass spectrometry (MS) as their hydrophobic nature typically requires stabilization in detergent micelles that are removed prior to analysis via collisional activation. There is however a practical limit to the amount of energy which can be applied, which often precludes subsequent characterization by top-down MS. To overcome this barrier, we have applied a modified Orbitrap Eclipse Tribrid mass spectrometer coupled to an infrared laser within a high-pressure linear ion trap. We show how tuning the intensity and time of incident photons enables liberation of membrane proteins from detergent micelles. Specifically, we relate the ease of micelle removal to the infrared absorption of detergents in both condensed and gas phases. Top-down MS via infrared multiphoton dissociation (IRMPD), results in good sequence coverage enabling unambiguous identification of membrane proteins and their complexes. By contrasting and comparing the fragmentation patterns of the ammonia channel with two class A GPCRs, we identify successive cleavage of adjacent amino acids within transmembrane domains. Using gas-phase molecular dynamics simulations, we show that areas prone to fragmentation maintain aspects of protein structure at increasing temperatures. Altogether, we propose a rationale to explain why and where in the protein fragment ions are generated.
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Affiliation(s)
- Corinne A. Lutomski
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Tarick J. El‐Baba
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | | | | | - Jack L. Bennett
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Neha V. Kalmankar
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Andrew Dolan
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
| | - Carla Kirschbaum
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
| | - Kim Greis
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
| | - Leonhard H. Urner
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
- Department of Chemistry and Chemical BiologyTU Dortmund UniversityDortmund44227Germany
| | | | - Hsin‐Yung Yen
- OMass TherapeuticsOxfordOX4 2GXUK
- Institute of Biological ChemistryAcademia SinicaTaipei115Taiwan
| | - Kevin Pagel
- Institute of Chemistry and BiochemistryFreie Universität BerlinBerlin14195Germany
- Fritz Haber Institute of the Max Planck SocietyBerlin14195Germany
| | | | | | - Carol V. Robinson
- Physical and Theoretical Chemistry Laboratory, Department of ChemistryUniversity of OxfordOxfordOX1 3QUUK
- Kavli Institute for Nanoscience Discovery, Dorothy Crowfoot Hodgkin BuildingUniversity of OxfordOxfordOX1 3QUUK
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15
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Wu D, Xu P, Kelly M, Ryan ET, Kováč P, Piszczek G. Mass photometry: A powerful tool for carbohydrates-proteins conjugation monitoring and glycoconjugates molecular mass determination. Glycoconj J 2023; 40:401-412. [PMID: 37392327 PMCID: PMC10374364 DOI: 10.1007/s10719-023-10126-7] [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] [Received: 05/04/2023] [Revised: 06/01/2023] [Accepted: 06/14/2023] [Indexed: 07/03/2023]
Abstract
Glycoconjugate vaccines are important additions to the existing means for prevention of diseases caused by bacterial and viral pathogens. Conjugating carbohydrates to proteins is a crucial step in the development of these vaccines. Traditional mass spectrometry techniques, such as MALDI-TOF and SELDI-TOF, have difficulties in detecting glycoconjugates with high molecular masses. Mass photometry (MP) is a single-molecule technique that has been recently developed, which allows mass measurements of individual molecules and generates mass distributions based on hundreds to thousands of these measurements. In this study, we evaluated the performance of MP in monitoring carbohydrate-protein conjugation reactions and characterization of conjugates. Three different glycoconjugates were prepared from carrier protein BSA, and one from a large protein complex, a virus capsid with 3.74 MDa molecular mass. The masses measured by MP were consistent with those obtained by SELDI-TOF-MS and SEC-MALS. The conjugation of BSA dimer to carbohydrate antigen was also successfully characterized. This study shows that the MP technique is a promising alternative to methods developed earlier for monitoring glycoconjugation reactions and characterization of glycoconjugates. It measures intact molecules in solution and it is highly accurate over a wide mass range. MP requires only a very small amount of sample and has no specific buffer constraints. Other MP advantages include minimal cost of consumables and rapid data collection and analysis. Its advantages over other methods make it a valuable tool for researchers in the glycoconjugation field.
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Affiliation(s)
- Di Wu
- Biophysics Core Facility, NHLBI, NIH, Bethesda, MD, 20892, USA.
| | - Peng Xu
- Laboratory of Bioorganic Chemistry, NIDDK, NIH, Bethesda, MD, 20892, USA
| | - Meagan Kelly
- Division of Infectious Diseases, Massachusetts General Hospital, Boston, MA, USA
| | - Edward T Ryan
- Division of Infectious Diseases, Massachusetts General Hospital, Boston, MA, USA
- Department of Medicine, Harvard Medical School, Boston, MA, USA
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public Health, Boston, MA, USA
| | - Pavol Kováč
- Laboratory of Bioorganic Chemistry, NIDDK, NIH, Bethesda, MD, 20892, USA
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16
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Reinhardt R, Leonard TA. A critical evaluation of protein kinase regulation by activation loop autophosphorylation. eLife 2023; 12:e88210. [PMID: 37470698 PMCID: PMC10359097 DOI: 10.7554/elife.88210] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 07/07/2023] [Indexed: 07/21/2023] Open
Abstract
Phosphorylation of proteins is a ubiquitous mechanism of regulating their function, localization, or activity. Protein kinases, enzymes that use ATP to phosphorylate protein substrates are, therefore, powerful signal transducers in eukaryotic cells. The mechanism of phosphoryl-transfer is universally conserved among protein kinases, which necessitates the tight regulation of kinase activity for the orchestration of cellular processes with high spatial and temporal fidelity. In response to a stimulus, many kinases enhance their own activity by autophosphorylating a conserved amino acid in their activation loop, but precisely how this reaction is performed is controversial. Classically, kinases that autophosphorylate their activation loop are thought to perform the reaction in trans, mediated by transient dimerization of their kinase domains. However, motivated by the recently discovered regulation mechanism of activation loop cis-autophosphorylation by a kinase that is autoinhibited in trans, we here review the various mechanisms of autoregulation that have been proposed. We provide a framework for critically evaluating biochemical, kinetic, and structural evidence for protein kinase dimerization and autophosphorylation, and share some thoughts on the implications of these mechanisms within physiological signaling networks.
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Affiliation(s)
- Ronja Reinhardt
- Max Perutz Labs, Vienna Biocenter Campus (VBC)ViennaAustria
- Medical University of Vienna, Center for Medical BiochemistryViennaAustria
| | - Thomas A Leonard
- Max Perutz Labs, Vienna Biocenter Campus (VBC)ViennaAustria
- Medical University of Vienna, Center for Medical BiochemistryViennaAustria
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17
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Haidar Y, Konermann L. Effects of Hydrogen/Deuterium Exchange on Protein Stability in Solution and in the Gas Phase. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023. [PMID: 37314114 DOI: 10.1021/jasms.3c00130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Mass spectrometry (MS)-based techniques are widely used for probing protein structure and dynamics in solution. H/D exchange (HDX)-MS is one of the most common approaches in this context. HDX is often considered to be a "benign" labeling method, in that it does not perturb protein behavior in solution. However, several studies have reported that D2O pushes unfolding equilibria toward the native state. The origin, and even the existence of this protein stabilization remain controversial. Here we conducted thermal unfolding assays in solution to confirm that deuterated proteins in D2O are more stable, with 2-4 K higher melting temperatures than unlabeled proteins in H2O. Previous studies tentatively attributed this phenomenon to strengthened H-bonds after deuteration, an effect that may arise from the lower zero-point vibrational energy of the deuterated species. Specifically, it was proposed that strengthened water-water bonds (W···W) in D2O lower the solubility of nonpolar side chains. The current work takes a broader view by noting that protein stability in solution also depends on water-protein (W···P) and protein-protein (P···P) H-bonds. To help unravel these contributions, we performed collision-induced unfolding (CIU) experiments on gaseous proteins generated by native electrospray ionization. CIU profiles of deuterated and unlabeled proteins were indistinguishable, implying that P···P contacts are insensitive to deuteration. Thus, protein stabilization in D2O is attributable to solvent effects, rather than alterations of intraprotein H-bonds. Strengthening of W···W contacts represents one possible explanation, but the stabilizing effect of D2O can also originate from weakened W···P bonds. Future work will be required to elucidate which of these two scenarios is correct, or if both contribute to protein stabilization in D2O. In any case, the often-repeated adage that "D-bonds are more stable than H-bonds" does not apply to intramolecular contacts in native proteins.
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Affiliation(s)
- Yousef Haidar
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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18
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Moore CC, Staroverov VN, Konermann L. Using Density Functional Theory for Testing the Robustness of Mobile-Proton Molecular Dynamics Simulations on Electrosprayed Ions: Structural Implications for Gaseous Proteins. J Phys Chem B 2023; 127:4061-4071. [PMID: 37116098 DOI: 10.1021/acs.jpcb.3c01581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
Current experiments only provide low-resolution information on gaseous protein ions generated by electrospray ionization (ESI). Molecular dynamics (MD) simulations can yield complementary insights. Unfortunately, conventional MD does not capture the mobile nature of protons in gaseous proteins. Mobile-proton MD (MPMD) overcomes this limitation. Earlier MPMD data at 300 K indicated that protein ions generated by "native" ESI retain solution-like structures with a hydrophobic core and zwitterionic exterior [Bakhtiari, M.; Konermann, L. J. Phys. Chem. B 2019, 123, 1784-1796]. MPMD redistributes protons using electrostatic and proton affinity calculations. The robustness of this approach has never been scrutinized. Here, we close this gap by benchmarking MPMD against density functional theory (DFT) at the B3LYP/6-31G* level, which is well suited for predicting proton affinities. The computational cost of DFT necessitated the use of small peptides. The MPMD energetic ranking of proton configurations was found to be consistent with DFT single-point energies, implying that MPMD can reliably identify favorable protonation sites. Peptide MPMD runs converged to DFT-optimized structures only when applying 300-500 K temperature cycling, which was necessary to prevent trapping in local minima. Temperature cycling MPMD was then applied to gaseous protein ions. Native ubiquitin converted to slightly expanded structures with a zwitterionic core and a nonpolar exterior. Our data suggest that such inside-out protein structures are intrinsically preferred in the gas phase, and that they form in ESI experiments after moderate collisional excitation. This is in contrast to native ESI (with minimal collisional excitation, simulated by MPMD at 300 K), where kinetic trapping promotes the survival of solution-like structures. In summary, this work validates the MPMD approach for simulations on gaseous peptides and proteins.
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Affiliation(s)
- Conrad C Moore
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Viktor N Staroverov
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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19
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Miller LM, Jarrold MF. Charge detection mass spectrometry for the analysis of viruses and virus-like particles. Essays Biochem 2023; 67:315-323. [PMID: 36062529 PMCID: PMC10842916 DOI: 10.1042/ebc20220101] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 08/11/2022] [Accepted: 08/19/2022] [Indexed: 11/17/2022]
Abstract
Heterogeneity usually restricts conventional mass spectrometry to molecular weights less than around a megadalton. As a single-particle technique, charge detection mass spectrometry (CDMS) overcomes this limitation. In CDMS, the mass-to-charge (m/z) ratio and charge are measured simultaneously for individual ions, giving a direct mass measurement for each ion. Recent applications include the analysis of viruses, virus-like particles, vaccines, heavily glycosylated proteins, and gene therapy vectors.
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Affiliation(s)
- Lohra M Miller
- Department of Chemistry, Indiana University, 800 E Kirkwood Ave, Bloomington 47401, Indiana
| | - Martin F Jarrold
- Department of Chemistry, Indiana University, 800 E Kirkwood Ave, Bloomington 47401, Indiana
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20
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Fiorentino F, Rotili D, Mai A. Native mass spectrometry-directed drug discovery: Recent advances in investigating protein function and modulation. Drug Discov Today 2023; 28:103548. [PMID: 36871843 DOI: 10.1016/j.drudis.2023.103548] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2022] [Revised: 02/15/2023] [Accepted: 02/28/2023] [Indexed: 03/07/2023]
Abstract
Native mass spectrometry (nMS) is a biophysical method for studying protein complexes and can provide insights into subunit stoichiometry and composition, protein-ligand, and protein-protein interactions (PPIs). These analyses are made possible by preserving non-covalent interactions in the gas phase, thereby allowing the analysis of proteins in their native state. Consequently, nMS has been increasingly applied in early drug discovery campaigns for the characterization of protein-drug interactions and the evaluation of PPI modulators. Here, we discuss recent developments in nMS-directed drug discovery and provide a timely perspective on the possible applications of this technology in drug discovery.
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Affiliation(s)
- Francesco Fiorentino
- Department of Drug Chemistry and Technologies, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy.
| | - Dante Rotili
- Department of Drug Chemistry and Technologies, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy.
| | - Antonello Mai
- Department of Drug Chemistry and Technologies, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy; Pasteur Institute, Cenci-Bolognetti Foundation, Sapienza University of Rome, Piazzale Aldo Moro 5, 00185 Rome, Italy
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21
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Richards NGJ, Bearne SL, Goto Y, Parker EJ. Reactivity and mechanism in chemical and synthetic biology. Philos Trans R Soc Lond B Biol Sci 2023; 378:20220023. [PMID: 36633278 PMCID: PMC9835593 DOI: 10.1098/rstb.2022.0023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Accepted: 11/28/2022] [Indexed: 01/13/2023] Open
Abstract
Physical organic chemistry and mechanistic thinking provide a strong intellectual framework for understanding the chemical logic of evolvable informational macromolecules and metabolic transformations in living organisms. These concepts have also led to numerous successes in designing and applying tools to delineate biological function in health and disease, chemical ecology and possible alternative chemistries employed by extraterrestrial life. A symposium at the 2020 Pacifichem meeting was scheduled in December 2020 to discuss designing and exploiting expanded genetic alphabets, methods to understand the biosynthesis of natural products and re-engineering primary metabolism in bacteria. The COVID-19 pandemic led to postponement of in-person discussions, with the symposium eventually being held on 20-21 December 2021 as an online event. This issue is a written record of work presented on biosynthetic pathways and enzyme catalysis, engineering microorganisms with new metabolic capabilities, and the synthesis of non-canonical, nucleobases for medical applications and for studies of alternate chemistries for living organisms. The variety of opinion pieces, reviews and original research articles provide a starting point for innovations that clarify how complex biological systems emerge from the rules of chemical reactivity and mechanism. This article is part of the themed issue 'Reactivity and mechanism in chemical and synthetic biology'.
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Affiliation(s)
- Nigel G. J. Richards
- School of Chemistry, Cardiff University, Park Place, Cardiff CF10 3AT, UK
- Foundation for Advanced Molecular Evolution, 13709 Progress Boulevard, Alachua, FL 32615, USA
| | - Stephen L. Bearne
- Department of Biochemistry and Molecular Biology, Dalhousie University, 5850 College Street, Halifax, Nova Scotia, Canada B3H 4R2
- Department of Chemistry, Dalhousie University, 6274 Coburg Road, Halifax, Nova Scotia, Canada B3H 4R2
| | - Yuki Goto
- Department of Chemistry, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
| | - Emily J. Parker
- Department of Chemistry, Victoria University of Wellington, Kelburn Parade, Wellington 6012, New Zealand
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22
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Wang B, Tieleman DP. Release of nanodiscs from charged nano-droplets in the electrospray ionization revealed by molecular dynamics simulations. Commun Chem 2023; 6:21. [PMID: 36717705 PMCID: PMC9886951 DOI: 10.1038/s42004-023-00818-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 01/19/2023] [Indexed: 01/31/2023] Open
Abstract
Electrospray ionization (ESI) is essential for application of mass spectrometry in biological systems, as it prevents the analyte being split into fragments. However, due to lack of a clear understanding of the mechanism of ESI, the interpretation of mass spectra is often ambiguous. This is a particular challenge for complex biological systems. Here, we focus on systems that include nanodiscs as membrane environment, which are essential for membrane proteins. We performed microsecond atomistic molecular dynamics simulations to study the release of nanodiscs from highly charged nano-droplets into the gas phase, the late stage of ESI. We observed two distinct major scenarios, highlighting the diversity of morphologies of gaseous product ions. Our simulations are in reasonable agreement with experimental results. Our work provides a detailed atomistic view of the ESI process of a heterogeneous system (lipid nanodisc), which may give insights into the interpretation of mass spectra of all lipid-protein systems.
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Affiliation(s)
- Beibei Wang
- grid.20513.350000 0004 1789 9964Centre for Advanced Materials Research, Beijing Normal University, Zhuhai, 519087 People’s Republic of China
| | - D. Peter Tieleman
- grid.22072.350000 0004 1936 7697Department of Biological Sciences and Centre for Molecular Simulation, University of Calgary, Calgary, T2N 1N4 Canada
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23
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Bennett SP, Crack JC, Puglisi R, Pastore A, Le Brun NE. Native mass spectrometric studies of IscSU reveal a concerted, sulfur-initiated mechanism of iron-sulfur cluster assembly. Chem Sci 2022; 14:78-95. [PMID: 36605734 PMCID: PMC9769115 DOI: 10.1039/d2sc04169c] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Accepted: 11/13/2022] [Indexed: 11/16/2022] Open
Abstract
Iron-sulfur (Fe-S) clusters are cofactors essential for life. Though the proteins that function in the assembly of Fe-S clusters are well known, details of the molecular mechanism are less well established. The Isc (iron-sulfur cluster) biogenesis apparatus is widespread in bacteria and is the closest homologue to the human system. Mutations in certain components of the human system lead to disease, and so further studies of this system could be important for developing strategies for medical treatments. We have studied two core components of the Isc biogenesis system: IscS, a cysteine desulfurase; and IscU, a scaffold protein on which clusters are built before subsequent transfer onto recipient apo-proteins. Fe2+-binding, sulfur transfer, and formation of a [2Fe-2S] was followed by a range of techniques, including time-resolved mass spectrometry, and intermediate and product species were unambiguously identified through isotopic substitution experiments using 57Fe and 34S. Under cluster synthesis conditions, sulfur adducts and the [2Fe-2S] cluster product readily accumulated on IscU, but iron adducts (other than the cluster itself) were not observed at physiologically relevant Fe2+ concentrations. Our data indicate that either Fe2+ or sulfur transfer can occur first, but that the transfer of sulfane sulfur (S0) to IscU must occur first if Zn2+ is bound to IscU, suggesting that it is the key step that initiates cluster assembly. Following this, [2Fe-2S] cluster formation is a largely concerted reaction once Fe2+ is introduced.
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Affiliation(s)
- Sophie P. Bennett
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East AngliaNorwich Research ParkNorwichNR4 7TJUK
| | - Jason C. Crack
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East AngliaNorwich Research ParkNorwichNR4 7TJUK
| | - Rita Puglisi
- The Wohl Institute, King's College London, Denmark Hill CampusLondon SE5 8AFUK
| | - Annalisa Pastore
- The Wohl Institute, King's College London, Denmark Hill CampusLondon SE5 8AFUK
| | - Nick E. Le Brun
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East AngliaNorwich Research ParkNorwichNR4 7TJUK
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24
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Konermann L, Haidar Y. Mechanism of Magic Number NaCl Cluster Formation from Electrosprayed Water Nanodroplets. Anal Chem 2022; 94:16491-16501. [DOI: 10.1021/acs.analchem.2c04141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Affiliation(s)
- Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Yousef Haidar
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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25
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Santambrogio C, Ponzini E, Grandori R. Native mass spectrometry for the investigation of protein structural (dis)order. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2022; 1870:140828. [PMID: 35926718 DOI: 10.1016/j.bbapap.2022.140828] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 06/24/2022] [Accepted: 07/29/2022] [Indexed: 06/15/2023]
Abstract
A central challenge in structural biology is represented by dynamic and heterogeneous systems, as typically represented by proteins in solution, with the extreme case of intrinsically disordered proteins (IDPs) [1-3]. These proteins lack a specific three-dimensional structure and have poorly organized secondary structure. For these reasons, they escape structural characterization by conventional biophysical methods. The investigation of these systems requires description of conformational ensembles, rather than of unique, defined structures or bundles of largely superimposable structures. Mass spectrometry (MS) has become a central tool in this field, offering a variety of complementary approaches to generate structural information on either folded or disordered proteins [4-6]. Two main categories of methods can be recognized. On one side, conformation-dependent reactions (such as cross-linking, covalent labeling, H/D exchange) are exploited to label molecules in solution, followed by the characterization of the labeling products by denaturing MS [7-11]. On the other side, non-denaturing ("native") MS can be used to directly explore the different conformational components in terms of geometry and structural compactness [12-16]. All these approaches have in common the capability to conjugate protein structure investigation with the peculiar analytical power of MS measurements, offering the possibility of assessing species distributions for folding and binding equilibria and the combination of both. These methods can be combined with characterization of noncovalent complexes [17, 18] and post-translational modifications [19-23]. This review focuses on the application of native MS to protein structure and dynamics investigation, with a general methodological section, followed by examples on specific proteins from our laboratory.
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Affiliation(s)
- Carlo Santambrogio
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy.
| | - Erika Ponzini
- Materials Science Department, University of Milano-Bicocca, Via R. Cozzi 55, 20125 Milan, Italy; COMiB Research Center, University of Milano-Bicocca, Via R. Cozzi 55, 20125 Milan, Italy
| | - Rita Grandori
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Piazza della Scienza 2, 20126 Milan, Italy.
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26
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Jarrold MF. Charge Detection Mass Spectrometry: Analysis of Gene Therapy Vectors. LCGC NORTH AMERICA 2022. [DOI: 10.56530/lcgc.na.wh5987h4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Conventional mass spectrometry is limited by heterogeneity to relatively small molecular weights from a biologics perspective. Charge detection mass spectrometry—where masses of individual ions are directly measured—overcomes this limitation and allows measurements into the gigadalton (GDa) range. An important application of this emerging technology is the analysis of gene therapy vectors. Their large size and complexity present analytical challenges that must be addressed for this promising therapeutic approach to reach its full potential.
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27
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Opening opportunities for K d determination and screening of MHC peptide complexes. Commun Biol 2022; 5:488. [PMID: 35606511 PMCID: PMC9127112 DOI: 10.1038/s42003-022-03366-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 04/13/2022] [Indexed: 01/15/2023] Open
Abstract
An essential element of adaptive immunity is selective binding of peptide antigens by major histocompatibility complex (MHC) class I proteins and their presentation to cytotoxic T lymphocytes. Using native mass spectrometry, we analyze the binding of peptides to an empty disulfide-stabilized HLA-A*02:01 molecule and, due to its unique stability, we determine binding affinities of complexes loaded with truncated or charge-reduced peptides. We find that the two anchor positions can be stabilized independently, and we further analyze the contribution of additional amino acid positions to the binding strength. As a complement to computational prediction tools, our method estimates binding strength of even low-affinity peptides to MHC class I complexes quickly and efficiently. It has huge potential to eliminate binding affinity biases and thus accelerate drug discovery in infectious diseases, autoimmunity, vaccine design, and cancer immunotherapy. The authors present a sensitive and rapid method to determine the binding strength of MHC class 1 peptide complexes using native mass spectrometry.
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28
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Aliyari E, Konermann L. Formation of Gaseous Peptide Ions from Electrospray Droplets: Competition between the Ion Evaporation Mechanism and Charged Residue Mechanism. Anal Chem 2022; 94:7713-7721. [PMID: 35587384 DOI: 10.1021/acs.analchem.2c01355] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The transfer of peptide ions from solution into the gas phase by electrospray ionization (ESI) is an integral component of mass spectrometry (MS)-based proteomics. The mechanisms whereby gaseous peptide ions are released from charged ESI nanodroplets remain unclear. This is in contrast to intact protein ESI, which has been the focus of detailed investigations using molecular dynamics (MD) simulations and other methods. Under acidic liquid chromatography/MS conditions, many peptides carry a solution charge of 3+ or 2+. Because of this pre-existing charge and their relatively small size, prevailing views suggest that peptides follow the ion evaporation mechanism (IEM). The IEM entails analyte ejection from ESI droplets, driven by electrostatic repulsion between the analyte and droplet. Surprisingly, recent peptide MD investigations reported a different behavior, that is, the release of peptide ions via droplet evaporation to dryness which represents the hallmark of the charged residue mechanism (CRM). Here, we resolved this conundrum by performing MD simulations on a common model peptide (bradykinin) in Rayleigh-charged aqueous droplets. The primary focus was on pH 2 conditions (bradykinin solution charge = 3+), but we also verified that our MD strategy captured pH-dependent charge state shifts seen in ESI-MS experiments. In agreement with earlier simulations, we found that droplets with initial radii of 1.5-3 nm predominantly release peptide ions via the CRM. In contrast, somewhat larger radii (4-5 nm) favor IEM behavior. It appears that these are the first MD data to unequivocally demonstrate the viability of peptide IEM events. Electrostatic arguments can account for the observed droplet size dependence. In summary, both CRM and IEM can be operative in peptide ESI-MS. The prevalence of one over the other mechanism depends on the droplet size distribution in the ESI plume.
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Affiliation(s)
- Elnaz Aliyari
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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29
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van Andel E, Roosjen M, van der Zanden S, Lange SC, Weijers D, Smulders MMJ, Savelkoul HFJ, Zuilhof H, Tijhaar EJ. Highly Specific Protein Identification by Immunoprecipitation-Mass Spectrometry Using Antifouling Microbeads. ACS APPLIED MATERIALS & INTERFACES 2022; 14:23102-23116. [PMID: 35536557 PMCID: PMC9136845 DOI: 10.1021/acsami.1c22734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/23/2021] [Accepted: 03/18/2022] [Indexed: 06/14/2023]
Abstract
A common method to study protein complexes is immunoprecipitation (IP), followed by mass spectrometry (thus labeled: IP-MS). IP-MS has been shown to be a powerful tool to identify protein-protein interactions. It is, however, often challenging to discriminate true protein interactors from contaminating ones. Here, we describe the preparation of antifouling azide-functionalized polymer-coated beads that can be equipped with an antibody of choice via click chemistry. We show the preparation of generic immunoprecipitation beads that target the green fluorescent protein (GFP) and show how they can be used in IP-MS experiments targeting two different GFP-fusion proteins. Our antifouling beads were able to efficiently identify relevant protein-protein interactions but with a strong reduction in unwanted nonspecific protein binding compared to commercial anti-GFP beads.
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Affiliation(s)
- Esther van Andel
- Laboratory
of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen, The Netherlands
- Cell
Biology and Immunology group, Wageningen
University, De Elst 1, 6709 PG Wageningen, The Netherlands
| | - Mark Roosjen
- Laboratory
of Biochemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Stef van der Zanden
- Cell
Biology and Immunology group, Wageningen
University, De Elst 1, 6709 PG Wageningen, The Netherlands
| | - Stefanie C. Lange
- Laboratory
of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Dolf Weijers
- Laboratory
of Biochemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Maarten M. J. Smulders
- Laboratory
of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Huub F. J. Savelkoul
- Cell
Biology and Immunology group, Wageningen
University, De Elst 1, 6709 PG Wageningen, The Netherlands
| | - Han Zuilhof
- Laboratory
of Organic Chemistry, Wageningen University, Stippeneng 4, 6708 WE Wageningen, The Netherlands
- School
of Pharmaceutical Sciences and Technology, Tianjin University, 92 Weijin Road, Tianjin 300072, People’s Republic of China
- Department
of Chemical and Materials Engineering, Faculty of Engineering, King Abdulaziz University, 21589 Jeddah, Saudi Arabia
| | - Edwin J. Tijhaar
- Cell
Biology and Immunology group, Wageningen
University, De Elst 1, 6709 PG Wageningen, The Netherlands
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30
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Snyder DT, Harvey SR, Wysocki VH. Surface-induced Dissociation Mass Spectrometry as a Structural Biology Tool. Chem Rev 2022; 122:7442-7487. [PMID: 34726898 PMCID: PMC9282826 DOI: 10.1021/acs.chemrev.1c00309] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Native mass spectrometry (nMS) is evolving into a workhorse for structural biology. The plethora of online and offline preparation, separation, and purification methods as well as numerous ionization techniques combined with powerful new hybrid ion mobility and mass spectrometry systems has illustrated the great potential of nMS for structural biology. Fundamental to the progression of nMS has been the development of novel activation methods for dissociating proteins and protein complexes to deduce primary, secondary, tertiary, and quaternary structure through the combined use of multiple MS/MS technologies. This review highlights the key features and advantages of surface collisions (surface-induced dissociation, SID) for probing the connectivity of subunits within protein and nucleoprotein complexes and, in particular, for solving protein structure in conjunction with complementary techniques such as cryo-EM and computational modeling. Several case studies highlight the significant role SID, and more generally nMS, will play in structural elucidation of biological assemblies in the future as the technology becomes more widely adopted. Cases are presented where SID agrees with solved crystal or cryoEM structures or provides connectivity maps that are otherwise inaccessible by "gold standard" structural biology techniques.
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Affiliation(s)
- Dalton T. Snyder
- Resource for Native Mass Spectrometry Guided Structural Biology, The Ohio State University, Columbus, OH 43210
| | - Sophie R. Harvey
- Resource for Native Mass Spectrometry Guided Structural Biology, The Ohio State University, Columbus, OH 43210,Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
| | - Vicki H. Wysocki
- Resource for Native Mass Spectrometry Guided Structural Biology, The Ohio State University, Columbus, OH 43210,Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210,Corresponding author:
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31
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Abstract
Charge detection mass spectrometry (CDMS) is a single-particle technique where the masses of individual ions are determined from simultaneous measurement of their mass-to-charge ratio (m/z) and charge. Masses are determined for thousands of individual ions, and then the results are binned to give a mass spectrum. Using this approach, accurate mass distributions can be measured for heterogeneous and high-molecular-weight samples that are usually not amenable to analysis by conventional mass spectrometry. Recent applications include heavily glycosylated proteins, protein complexes, protein aggregates such as amyloid fibers, infectious viruses, gene therapies, vaccines, and vesicles such as exosomes.
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Affiliation(s)
- Martin F Jarrold
- Chemistry Department, Indiana University, 800 E. Kirkwood Avenue, Bloomington, Indiana 47404, United States
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32
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Gavriilidou AFM, Sokratous K, Yen HY, De Colibus L. High-Throughput Native Mass Spectrometry Screening in Drug Discovery. Front Mol Biosci 2022; 9:837901. [PMID: 35495635 PMCID: PMC9047894 DOI: 10.3389/fmolb.2022.837901] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2021] [Accepted: 02/15/2022] [Indexed: 12/15/2022] Open
Abstract
The design of new therapeutic molecules can be significantly informed by studying protein-ligand interactions using biophysical approaches directly after purification of the protein-ligand complex. Well-established techniques utilized in drug discovery include isothermal titration calorimetry, surface plasmon resonance, nuclear magnetic resonance spectroscopy, and structure-based drug discovery which mainly rely on protein crystallography and, more recently, cryo-electron microscopy. Protein-ligand complexes are dynamic, heterogeneous, and challenging systems that are best studied with several complementary techniques. Native mass spectrometry (MS) is a versatile method used to study proteins and their non-covalently driven assemblies in a native-like folded state, providing information on binding thermodynamics and stoichiometry as well as insights on ternary and quaternary protein structure. Here, we discuss the basic principles of native mass spectrometry, the field’s recent progress, how native MS is integrated into a drug discovery pipeline, and its future developments in drug discovery.
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33
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Bianchi G, Mangiagalli M, Barbiroli A, Longhi S, Grandori R, Santambrogio C, Brocca S. Distribution of Charged Residues Affects the Average Size and Shape of Intrinsically Disordered Proteins. Biomolecules 2022; 12:biom12040561. [PMID: 35454150 PMCID: PMC9031945 DOI: 10.3390/biom12040561] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Revised: 04/05/2022] [Accepted: 04/07/2022] [Indexed: 12/29/2022] Open
Abstract
Intrinsically disordered proteins (IDPs) are ensembles of interconverting conformers whose conformational properties are governed by several physico-chemical factors, including their amino acid composition and the arrangement of oppositely charged residues within the primary structure. In this work, we investigate the effects of charge patterning on the average compactness and shape of three model IDPs with different proline content. We model IDP ensemble conformations as ellipsoids, whose size and shape are calculated by combining data from size-exclusion chromatography and native mass spectrometry. For each model IDP, we analyzed the wild-type protein and two synthetic variants with permuted positions of charged residues, where positive and negative amino acids are either evenly distributed or segregated. We found that charge clustering induces remodeling of the conformational ensemble, promoting compaction and/or increasing spherical shape. Our data illustrate that the average shape and volume of the ensembles depend on the charge distribution. The potential effect of other factors, such as chain length, number of proline residues, and secondary structure content, is also discussed. This methodological approach is a straightforward way to model IDP average conformation and decipher the salient sequence attributes influencing IDP structural properties.
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Affiliation(s)
- Greta Bianchi
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, 20126 Milan, Italy; (G.B.); (M.M.); (R.G.)
| | - Marco Mangiagalli
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, 20126 Milan, Italy; (G.B.); (M.M.); (R.G.)
| | - Alberto Barbiroli
- Departement of Food, Environmental and Nutritional Sciences, University of Milan, 20133 Milan, Italy;
| | - Sonia Longhi
- Laboratory Architecture et Fonction des Macromolécules Biologiques (AFMB), UMR 7257, Centre National de la Recherche Scientifique (CNRS), Aix Marseille University, 13288 Marseille, France;
| | - Rita Grandori
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, 20126 Milan, Italy; (G.B.); (M.M.); (R.G.)
| | - Carlo Santambrogio
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, 20126 Milan, Italy; (G.B.); (M.M.); (R.G.)
- Correspondence: (C.S.); (S.B.); Tel.: +39-02-6448-3363 (C.S.); +39-02-6448-3518 (S.B.)
| | - Stefania Brocca
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, 20126 Milan, Italy; (G.B.); (M.M.); (R.G.)
- Correspondence: (C.S.); (S.B.); Tel.: +39-02-6448-3363 (C.S.); +39-02-6448-3518 (S.B.)
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34
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Sun J, Li W, Gross ML. Advances in mass spectrometry-based footprinting of membrane proteins. Proteomics 2022; 22:e2100222. [PMID: 35290716 PMCID: PMC10493193 DOI: 10.1002/pmic.202100222] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 02/24/2022] [Accepted: 02/25/2022] [Indexed: 11/09/2022]
Abstract
Structural biology is entering an exciting time where many new high-resolution structures of large complexes and membrane proteins (MPs) are determined regularly. These advances have been driven by over 15 years of technological improvements, first in macromolecular crystallography, and recently in cryo-electron microscopy. Obtaining information about MP higher order structure and interactions is also a frontier, important but challenging owing to their unique properties and the need to choose suitable detergents/lipids for their study. The development of mass spectrometry (MS), both instruments and methodology in the past 10 years, has also advanced it as a complementary method to study MP structure and interactions. In this review, we discuss advances in MS-based footprinting for MPs and highlight recent methodologies that offer new promise for MP study by chemical footprinting and mass spectrometry.
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Affiliation(s)
- Jie Sun
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Weikai Li
- Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Michael L Gross
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri, USA
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35
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Tucholski T, Ge Y. Fourier-transform ion cyclotron resonance mass spectrometry for characterizing proteoforms. MASS SPECTROMETRY REVIEWS 2022; 41:158-177. [PMID: 32894796 PMCID: PMC7936991 DOI: 10.1002/mas.21653] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 08/26/2020] [Accepted: 08/26/2020] [Indexed: 05/05/2023]
Abstract
Proteoforms contribute functional diversity to the proteome and aberrant proteoforms levels have been implicated in biological dysfunction and disease. Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), with its ultrahigh mass-resolving power, mass accuracy, and versatile tandem MS capabilities, has empowered top-down, middle-down, and native MS-based approaches for characterizing proteoforms and their complexes in biological systems. Herein, we review the features which make FT-ICR MS uniquely suited for measuring proteoform mass with ultrahigh resolution and mass accuracy; obtaining in-depth proteoform sequence coverage with expansive tandem MS capabilities; and unambiguously identifying and localizing post-translational and noncovalent modifications. We highlight examples from our body of work in which we have quantified and comprehensively characterized proteoforms from cardiac and skeletal muscle to better understand conditions such as chronic heart failure, acute myocardial infarction, and sarcopenia. Structural characterization of monoclonal antibodies and their proteoforms by FT-ICR MS and emerging applications, such as native top-down FT-ICR MS and high-throughput top-down FT-ICR MS-based proteomics at 21 T, are also covered. Historically, the information gleaned from FT-ICR MS analyses have helped provide biological insights. We predict FT-ICR MS will continue to enable the study of proteoforms of increasing size from increasingly complex endogenous mixtures and facilitate the benchmarking of sensitive and specific assays for clinical diagnostics. © 2020 John Wiley & Sons Ltd. Mass Spec Rev.
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Affiliation(s)
- Trisha Tucholski
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706
| | - Ying Ge
- Department of Chemistry, University of Wisconsin-Madison, Madison, WI, 53706
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, WI, 53706
- Human Proteomics Program, University of Wisconsin-Madison, Madison, WI, 53705
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36
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Townsend JA, Sanders HM, Rolland AD, Park CK, Horton NC, Prell JS, Wang J, Marty MT. Influenza AM2 Channel Oligomerization Is Sensitive to Its Chemical Environment. Anal Chem 2021; 93:16273-16281. [PMID: 34813702 DOI: 10.1021/acs.analchem.1c04660] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Viroporins are small viral ion channels that play important roles in the viral infection cycle and are proven antiviral drug targets. Matrix protein 2 from influenza A (AM2) is the best-characterized viroporin, and the current paradigm is that AM2 forms monodisperse tetramers. Here, we used native mass spectrometry and other techniques to characterize the oligomeric state of both the full-length and transmembrane (TM) domain of AM2 in a variety of different pH and detergent conditions. Unexpectedly, we discovered that AM2 formed a range of different oligomeric complexes that were strongly influenced by the local chemical environment. Native mass spectrometry of AM2 in nanodiscs with different lipids showed that lipids also affected the oligomeric states of AM2. Finally, nanodiscs uniquely enabled the measurement of amantadine binding stoichiometries to AM2 in the intact lipid bilayer. These unexpected results reveal that AM2 can form a wider range of oligomeric states than previously thought possible, which may provide new potential mechanisms of influenza pathology and pharmacology.
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Affiliation(s)
- Julia A Townsend
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
| | - Henry M Sanders
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
| | - Amber D Rolland
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, United States.,Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, United States
| | - Chad K Park
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, United States
| | - Nancy C Horton
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, United States
| | - James S Prell
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, United States.,Materials Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Jun Wang
- Department of Pharmacology and Toxicology, The University of Arizona, Tucson, Arizona 85721, United States.,Bio5 Institute, The University of Arizona, Tucson, Arizona 85721, United States
| | - Michael T Marty
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States.,Bio5 Institute, The University of Arizona, Tucson, Arizona 85721, United States
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37
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Macias LA, Sipe SN, Santos IC, Bashyal A, Mehaffey MR, Brodbelt JS. Influence of Primary Structure on Fragmentation of Native-Like Proteins by Ultraviolet Photodissociation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:2860-2873. [PMID: 34714071 PMCID: PMC8639798 DOI: 10.1021/jasms.1c00269] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Analysis of native-like protein structures in the gas phase via native mass spectrometry and auxiliary techniques has become a powerful tool for structural biology applications. In combination with ultraviolet photodissociation (UVPD), native top-down mass spectrometry informs backbone flexibility, topology, hydrogen bonding networks, and conformational changes in protein structure. Although it is known that the primary structure affects dissociation of peptides and proteins in the gas phase, its effect on the types and locations of backbone cleavages promoted by UVPD and concomitant influence on structural characterization of native-like proteins is not well understood. Here, trends in the fragmentation of native-like proteins were evaluated by tracking the propensity of 10 fragment types (a, a+1, b, c, x, x+1, y, y-1, Y, and z) in relation to primary structure in a native-top down UVPD data set encompassing >9600 fragment ions. Differing fragmentation trends are reported for the production of distinct fragment types, attributed to a combination of both direct dissociation pathways from excited electronic states and those surmised to involve intramolecular vibrational energy redistribution after internal conversion. The latter pathways were systematically evaluated to evince the role of proton mobility in the generation of "CID-like" fragments through UVPD, providing pertinent insight into the characterization of native-like proteins. Fragmentation trends presented here are envisioned to enhance analysis of the protein higher-order structure or augment scoring algorithms in the high-throughput analysis of intact proteins.
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Affiliation(s)
- Luis A Macias
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Sarah N Sipe
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Inês C Santos
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Aarti Bashyal
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - M Rachel Mehaffey
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
| | - Jennifer S Brodbelt
- Department of Chemistry, The University of Texas at Austin, Austin, Texas 78712, United States
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38
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Aliyari E, Konermann L. Atomistic Insights into the Formation of Nonspecific Protein Complexes during Electrospray Ionization. Anal Chem 2021; 93:12748-12757. [PMID: 34494821 DOI: 10.1021/acs.analchem.1c02836] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Native electrospray ionization (ESI)-mass spectrometry (MS) is widely used for the detection and characterization of multi-protein complexes. A well-known problem with this approach is the possible occurrence of nonspecific protein clustering in the ESI plume. This effect can distort the results of binding affinity measurements, and it can even generate gas-phase complexes from proteins that are strictly monomeric in bulk solution. By combining experiments and molecular dynamics (MD) simulations, the current work for the first time provides detailed insights into the ESI clustering of proteins. Using ubiquitin as a model system, we demonstrate how the entrapment of more than one protein molecule in an ESI droplet can generate nonspecific clusters (e.g., dimers or trimers) via solvent evaporation to dryness. These events are in line with earlier proposals, according to which protein clustering is associated with the charged residue model (CRM). MD simulations on cytochrome c (which carries a large intrinsic positive charge) confirmed the viability of this CRM avenue. In addition, the cytochrome c data uncovered an alternative mechanism where protein-protein contacts were formed early within ESI droplets, followed by cluster ejection from the droplet surface. This second pathway is consistent with the ion evaporation model (IEM). The observation of these IEM events for large protein clusters is unexpected because the IEM has been thought to be associated primarily with low-molecular-weight analytes. In all cases, our MD simulations produced protein clusters that were stabilized by intermolecular salt bridges. The MD-generated charge states agreed with experiments. Overall, this work reveals that ESI-induced protein clustering does not follow a tightly orchestrated pathway but can proceed along different avenues.
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Affiliation(s)
- Elnaz Aliyari
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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Bai B, Vanderwall D, Li Y, Wang X, Poudel S, Wang H, Dey KK, Chen PC, Yang K, Peng J. Proteomic landscape of Alzheimer's Disease: novel insights into pathogenesis and biomarker discovery. Mol Neurodegener 2021; 16:55. [PMID: 34384464 PMCID: PMC8359598 DOI: 10.1186/s13024-021-00474-z] [Citation(s) in RCA: 90] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Accepted: 07/18/2021] [Indexed: 12/15/2022] Open
Abstract
Mass spectrometry-based proteomics empowers deep profiling of proteome and protein posttranslational modifications (PTMs) in Alzheimer's disease (AD). Here we review the advances and limitations in historic and recent AD proteomic research. Complementary to genetic mapping, proteomic studies not only validate canonical amyloid and tau pathways, but also uncover novel components in broad protein networks, such as RNA splicing, development, immunity, membrane transport, lipid metabolism, synaptic function, and mitochondrial activity. Meta-analysis of seven deep datasets reveals 2,698 differentially expressed (DE) proteins in the landscape of AD brain proteome (n = 12,017 proteins/genes), covering 35 reported AD genes and risk loci. The DE proteins contain cellular markers enriched in neurons, microglia, astrocytes, oligodendrocytes, and epithelial cells, supporting the involvement of diverse cell types in AD pathology. We discuss the hypothesized protective or detrimental roles of selected DE proteins, emphasizing top proteins in "amyloidome" (all biomolecules in amyloid plaques) and disease progression. Comprehensive PTM analysis represents another layer of molecular events in AD. In particular, tau PTMs are correlated with disease stages and indicate the heterogeneity of individual AD patients. Moreover, the unprecedented proteomic coverage of biofluids, such as cerebrospinal fluid and serum, procures novel putative AD biomarkers through meta-analysis. Thus, proteomics-driven systems biology presents a new frontier to link genotype, proteotype, and phenotype, accelerating the development of improved AD models and treatment strategies.
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Affiliation(s)
- Bing Bai
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
- Current address: Center for Precision Medicine, Department of Laboratory Medicine, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Jiangsu 210008 Nanjing, China
| | - David Vanderwall
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
| | - Yuxin Li
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
- Center for Proteomics and Metabolomics, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
| | - Xusheng Wang
- Center for Proteomics and Metabolomics, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
- Current address: Department of Biology, University of North Dakota, ND 58202 Grand Forks, USA
| | - Suresh Poudel
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
- Center for Proteomics and Metabolomics, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
| | - Hong Wang
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
- Center for Proteomics and Metabolomics, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
| | - Kaushik Kumar Dey
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
| | - Ping-Chung Chen
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
| | - Ka Yang
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
| | - Junmin Peng
- Departments of Structural Biology and Developmental Neurobiology, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
- Center for Proteomics and Metabolomics, St. Jude Children’s Research Hospital, 38105 Memphis, TN USA
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Hoi KK, Bada Juarez JF, Judge PJ, Yen HY, Wu D, Vinals J, Taylor GF, Watts A, Robinson CV. Detergent-free Lipodisq Nanoparticles Facilitate High-Resolution Mass Spectrometry of Folded Integral Membrane Proteins. NANO LETTERS 2021; 21:2824-2831. [PMID: 33787280 PMCID: PMC8050825 DOI: 10.1021/acs.nanolett.0c04911] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 03/04/2021] [Indexed: 05/04/2023]
Abstract
Integral membrane proteins pose considerable challenges to mass spectrometry (MS) owing to the complexity and diversity of the components in their native environment. Here, we use native MS to study the post-translational maturation of bacteriorhodopsin (bR) and archaerhodopsin-3 (AR3), using both octyl-glucoside detergent micelles and lipid-based nanoparticles. A lower collision energy was required to obtain well-resolved spectra for proteins in styrene-maleic acid copolymer (SMA) Lipodisqs than in membrane scaffold protein (MSP) Nanodiscs. By comparing spectra of membrane proteins prepared using the different membrane mimetics, we found that SMA may favor selective solubilization of correctly folded proteins and better preserve native lipid interactions than other membrane mimetics. Our spectra reveal the correlation between the post-translation modifications (PTMs), lipid-interactions, and protein-folding states of bR, providing insights into the process of maturation of the photoreceptor proteins.
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Affiliation(s)
- Kin Kuan Hoi
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Juan Francisco Bada Juarez
- Department
of Biochemistry, Biomembrane Structure Unit, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Peter J. Judge
- Department
of Biochemistry, Biomembrane Structure Unit, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Hsin-Yung Yen
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
- OMass
Therapeutics, The Schrödinger
Building, Oxford Science Park, Oxford OX4
4GE, United Kingdom
| | - Di Wu
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
| | - Javier Vinals
- Department
of Biochemistry, Biomembrane Structure Unit, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Garrick F. Taylor
- Department
of Biochemistry, Biomembrane Structure Unit, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Anthony Watts
- Department
of Biochemistry, Biomembrane Structure Unit, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Carol V. Robinson
- Department
of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom
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Konermann L, Aliyari E, Lee JH. Mobile Protons Limit the Stability of Salt Bridges in the Gas Phase: Implications for the Structures of Electrosprayed Protein Ions. J Phys Chem B 2021; 125:3803-3814. [PMID: 33848419 DOI: 10.1021/acs.jpcb.1c00944] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Electrosprayed protein ions can retain native-like conformations. The intramolecular contacts that stabilize these compact gas-phase structures remain poorly understood. Recent work has uncovered abundant salt bridges in electrosprayed proteins. Salt bridges are zwitterionic BH+/A- contacts. The low dielectric constant in the vacuum strengthens electrostatic interactions, suggesting that salt bridges could be a key contributor to the retention of compact protein structures. A problem with this assertion is that H+ are mobile, such that H+ transfer can convert salt bridges into neutral B0/HA0 contacts. This possible salt bridge annihilation puts into question the role of zwitterionic motifs in the gas phase, and it calls for a detailed analysis of BH+/A- versus B0/HA0 interactions. Here, we investigate this issue using molecular dynamics (MD) simulations and electrospray experiments. MD data for short model peptides revealed that salt bridges with static H+ have dissociation energies around 700 kJ mol-1. The corresponding B0/HA0 contacts are 1 order of magnitude weaker. When considering the effects of mobile H+, BH+/A- bond energies were found to be between these two extremes, confirming that H+ migration can significantly weaken salt bridges. Next, we examined the protein ubiquitin under collision-induced unfolding (CIU) conditions. CIU simulations were conducted using three different MD models: (i) Positive-only runs with static H+ did not allow for salt bridge formation and produced highly expanded CIU structures. (ii) Zwitterionic runs with static H+ resulted in abundant salt bridges, culminating in much more compact CIU structures. (iii) Mobile H+ simulations allowed for the dynamic formation/annihilation of salt bridges, generating CIU structures intermediate between scenarios (i) and (ii). Our results uncover that mobile H+ limit the stabilizing effects of salt bridges in the gas phase. Failure to consider the effects of mobile H+ in MD simulations will result in unrealistic outcomes under CIU conditions.
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Affiliation(s)
- Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Elnaz Aliyari
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Justin H Lee
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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Kwan V, O’Dwyer R, Laur D, Tan J, Consta S. Relation between Ejection Mechanism and Ion Abundance in the Electric Double Layer of Droplets. J Phys Chem A 2021; 125:2954-2966. [DOI: 10.1021/acs.jpca.1c01522] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Victor Kwan
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Ryan O’Dwyer
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - David Laur
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Jiahua Tan
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
- College of Chemistry, Nankai University, Tianjin 300071, P. R. China
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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Agasid MT, Sørensen L, Urner LH, Yan J, Robinson CV. The Effects of Sodium Ions on Ligand Binding and Conformational States of G Protein-Coupled Receptors-Insights from Mass Spectrometry. J Am Chem Soc 2021; 143:4085-4089. [PMID: 33711230 PMCID: PMC7995251 DOI: 10.1021/jacs.0c11837] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
![]()
The use of mass spectrometry
to investigate proteins is now well
established and provides invaluable information for both soluble and
membrane protein assemblies. Maintaining transient noncovalent interactions
under physiological conditions, however, remains challenging. Here,
using nanoscale electrospray ionization emitters, we establish conditions
that enable mass spectrometry of two G protein-coupled receptors (GPCR)
from buffers containing high concentrations of sodium ions. For the
Class A GPCR, the adenosine 2A receptor, we observe ligand-induced
changes to sodium binding of the receptor at the level of individual
sodium ions. We find that antagonists promote sodium binding while
agonists attenuate sodium binding. These findings are in line with
high-resolution X-ray crystallography wherein only inactive conformations
retain sodium ions in allosteric binding pockets. For the glucagon
receptor (a Class B GPCR) we observed enhanced ligand binding in electrospray
buffers containing high concentrations of sodium, as opposed to ammonium
acetate buffers. A combination of native and -omics mass spectrometry
revealed the presence of a lipophilic negative allosteric modulator.
These experiments highlight the advantages of implementing native
mass spectrometry, from electrospray buffers containing high concentrations
of physiologically relevant salts, to inform on allosteric ions or
ligands with the potential to define their roles on GPCR function.
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Affiliation(s)
- Mark T Agasid
- Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Lars Sørensen
- Global Research Technologies, Novo Nordisk A/S, Novo Nordisk Park, Måløv 2760, Denmark
| | - Leonhard H Urner
- Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
| | - Jun Yan
- Global Research Technologies, Novo Nordisk A/S, Novo Nordisk Park, Måløv 2760, Denmark
| | - Carol V Robinson
- Department of Chemistry, University of Oxford, 12 Mansfield Road, Oxford OX1 3TA, U.K
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Martin LM, Konermann L. Sulfolane-Induced Supercharging of Electrosprayed Salt Clusters: An Experimental/Computational Perspective. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:486-496. [PMID: 33334096 DOI: 10.1021/jasms.0c00377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
It is well-known that supercharging agents (SCAs) such as sulfolane enhance the electrospray ionization (ESI) charge states of proteins, although the mechanistic origins of this effect remain contentious. Only very few studies have explored SCA effects on analytes other than proteins or peptides. This work examines how sulfolane affects electrosprayed NaI salt clusters. Such alkali metal halide clusters have played a key role for earlier ESI mechanistic studies, making them interesting targets for supercharging investigations. ESI of aqueous NaI solutions predominantly generated singly charged [NanI(n-1)]+ clusters. The addition of sulfolane resulted in abundant doubly charged [NanI(n-2)Sulfolanes]2+ species. These experimental data for the first time demonstrate that electrosprayed salt clusters can undergo supercharging. Molecular dynamics (MD) simulations of aqueous ESI nanodroplets containing Na+/I- with and without sulfolane were conducted to obtain atomistic insights into the supercharging mechanism. The simulations produced [NanIi]z+ and [NanIiSulfolanes]z+ clusters similar to those observed experimentally. The MD trajectories demonstrated that these clusters were released into the gas phase upon droplet evaporation to dryness, in line with the charged residue model. Sulfolane was found to evaporate much more slowly than water. This slow evaporation, in conjunction with the large dipole moment of sulfolane, resulted in electrostatic stabilization of the shrinking ESI droplets and the final clusters. Hence, charge-dipole stabilization causes the sulfolane-containing droplets and clusters to retain more charge, thereby providing the mechanistic foundation of salt cluster supercharging.
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Affiliation(s)
- Leanne M Martin
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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45
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Norris CE, Keener JE, Perera SMDC, Weerasinghe N, Fried SDE, Resager WC, Rohrbough JG, Brown MF, Marty MT. Native Mass Spectrometry Reveals the Simultaneous Binding of Lipids and Zinc to Rhodopsin. INTERNATIONAL JOURNAL OF MASS SPECTROMETRY 2021; 460:116477. [PMID: 33281496 PMCID: PMC7709953 DOI: 10.1016/j.ijms.2020.116477] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Rhodopsin, a prototypical G-protein-coupled receptor, is responsible for scoptic vision at low-light levels. Although rhodopsin's photoactivation cascade is well understood, it remains unclear how lipid and zinc binding to the receptor are coupled. Using native mass spectrometry, we developed a novel data analysis strategy to deconvolve zinc and lipid bound to the proteoforms of rhodopsin and investigated the allosteric interaction between lipids and zinc binding. We discovered that phosphatidylcholine bound to rhodopsin with a greater affinity than phosphatidylserine or phosphatidylethanolamine, and that binding of all lipids was influenced by zinc but with different effects. In contrast, zinc binding was relatively unperturbed by lipids. Overall, these data reveal that lipid binding can be strongly and differentially influenced by metal ions.
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Affiliation(s)
- Carolanne E. Norris
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721
| | - James E. Keener
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721
| | | | - Nipuna Weerasinghe
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721
| | - Steven D. E. Fried
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721
| | - William C. Resager
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721
| | - James G. Rohrbough
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721
| | - Michael F. Brown
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721
- Department of Physics, University of Arizona, Tucson, AZ 85721
- Bio5 Institute, University of Arizona, Tucson, AZ 85721
| | - Michael T. Marty
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721
- Bio5 Institute, University of Arizona, Tucson, AZ 85721
- Corresponding Author Dr. Michael T. Marty, 1306 E. University Blvd., Tucson, AZ 85721,
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46
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Pagano L, Toto A, Malagrinò F, Visconti L, Jemth P, Gianni S. Double Mutant Cycles as a Tool to Address Folding, Binding, and Allostery. Int J Mol Sci 2021; 22:E828. [PMID: 33467625 PMCID: PMC7830974 DOI: 10.3390/ijms22020828] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 01/13/2021] [Accepted: 01/13/2021] [Indexed: 11/16/2022] Open
Abstract
Quantitative measurement of intramolecular and intermolecular interactions in protein structure is an elusive task, not easy to address experimentally. The phenomenon denoted 'energetic coupling' describes short- and long-range interactions between two residues in a protein system. A powerful method to identify and quantitatively characterize long-range interactions and allosteric networks in proteins or protein-ligand complexes is called double-mutant cycles analysis. In this review we describe the thermodynamic principles and basic equations that underlie the double mutant cycle methodology, its fields of application and latest employments, and caveats and pitfalls that the experimentalists must consider. In particular, we show how double mutant cycles can be a powerful tool to investigate allosteric mechanisms in protein binding reactions as well as elusive states in protein folding pathways.
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Affiliation(s)
- Livia Pagano
- Istituto Pasteur—Fondazione Cenci Bolognetti, Dipartimento di Scienze Biochimiche ‘A. Rossi Fanelli’ and Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, 00185 Rome, Italy; (L.P.); (A.T.); (F.M.); (L.V.)
| | - Angelo Toto
- Istituto Pasteur—Fondazione Cenci Bolognetti, Dipartimento di Scienze Biochimiche ‘A. Rossi Fanelli’ and Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, 00185 Rome, Italy; (L.P.); (A.T.); (F.M.); (L.V.)
| | - Francesca Malagrinò
- Istituto Pasteur—Fondazione Cenci Bolognetti, Dipartimento di Scienze Biochimiche ‘A. Rossi Fanelli’ and Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, 00185 Rome, Italy; (L.P.); (A.T.); (F.M.); (L.V.)
| | - Lorenzo Visconti
- Istituto Pasteur—Fondazione Cenci Bolognetti, Dipartimento di Scienze Biochimiche ‘A. Rossi Fanelli’ and Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, 00185 Rome, Italy; (L.P.); (A.T.); (F.M.); (L.V.)
| | - Per Jemth
- Department of Medical Biochemistry and Microbiology, Uppsala University, SE-75123 Uppsala, Sweden
| | - Stefano Gianni
- Istituto Pasteur—Fondazione Cenci Bolognetti, Dipartimento di Scienze Biochimiche ‘A. Rossi Fanelli’ and Istituto di Biologia e Patologia Molecolari del CNR, Sapienza Università di Roma, 00185 Rome, Italy; (L.P.); (A.T.); (F.M.); (L.V.)
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47
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Affiliation(s)
- Tobias
P. Wörner
- Biomolecular
Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular
Research and Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584
CH Utrecht, The Netherlands
- Netherlands
Proteomics Center, Padualaan
8, 3584 CH Utrecht, The Netherlands
| | - Tatiana M. Shamorkina
- Biomolecular
Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular
Research and Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584
CH Utrecht, The Netherlands
- Netherlands
Proteomics Center, Padualaan
8, 3584 CH Utrecht, The Netherlands
| | - Joost Snijder
- Biomolecular
Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular
Research and Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584
CH Utrecht, The Netherlands
- Netherlands
Proteomics Center, Padualaan
8, 3584 CH Utrecht, The Netherlands
| | - Albert J. R. Heck
- Biomolecular
Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular
Research and Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584
CH Utrecht, The Netherlands
- Netherlands
Proteomics Center, Padualaan
8, 3584 CH Utrecht, The Netherlands
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48
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Sever AIM, Yin V, Konermann L. Interrogating the Quaternary Structure of Noncanonical Hemoglobin Complexes by Electrospray Mass Spectrometry and Collision-Induced Dissociation. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:270-280. [PMID: 33124417 DOI: 10.1021/jasms.0c00320] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Various activation methods are available for the fragmentation of gaseous protein complexes produced by electrospray ionization (ESI). Such experiments can potentially yield insights into quaternary structure. Collision-induced dissociation (CID) is the most widely used fragmentation technique. Unfortunately, CID of protein complexes is dominated by the ejection of highly charged monomers, a process that does not yield any structural insights. Using hemoglobin (Hb) as a model system, this work examines under what conditions CID generates structurally informative subcomplexes. Native ESI mainly produced tetrameric Hb ions. In addition, "noncanonical" hexameric and octameric complexes were observed. CID of all these species [(αβ)2, (αβ)3, and (αβ)4] predominantly generated highly charged monomers. In addition, we observed hexamer → tetramer + dimer dissociation, implying that hexamers have a tetramer··dimer architecture. Similarly, the observation of octamer → two tetramer dissociation revealed that octamers have a tetramer··tetramer composition. Gas-phase candidate structures of Hb assemblies were produced by molecular dynamics (MD) simulations. Ion mobility spectrometry was used to identify the most likely candidates. Our data reveal that the capability of CID to produce structurally informative subcomplexes depends on the fate of protein-protein interfaces after transfer into the gas phase. Collapse of low affinity interfaces conjoins the corresponding subunits and favors CID via monomer ejection. Structurally informative subcomplexes are formed only if low affinity interfaces do not undergo a major collapse. However, even in these favorable cases CID is still dominated by monomer ejection, requiring careful analysis of the experimental data for the identification of structurally informative subcomplexes.
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Affiliation(s)
- Alexander I M Sever
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Victor Yin
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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49
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Kwan V, Consta S. Molecular Characterization of the Surface Excess Charge Layer in Droplets. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:33-45. [PMID: 32597645 DOI: 10.1021/jasms.0c00053] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The surface excess charge layer (SECL) in droplets has often been associated with distinct chemistry. We examine the effect of the nature of ions in the composition and structure of SECL by using molecular dynamics. We find that in the presence of simple ions the thickness of SECL is invariant not only with respect to droplet size but also with respect to the nature of the ions. In the presence of simple ions, this layer has a thickness of ∼1.5-1.7 nm but in the presence of macroions it may extend to ∼2.0 nm. The proportion of ions contained in SECL depends on the nature of the ions and the droplet size. For the same droplet size, I- and model H3O+ ions show considerably higher concentration than Na+ and Cl- ions. We identify the maximum ion concentration region, which, in nanodrops, may partially overlap with SECL. As the relative shape fluctuations decrease when microdrop size is approached, the overlap between SECL and maximum ion concentration region increases. We suggest the extension of the bilayer droplet structure assumed in the equilibrium partitioning model of Enke to include the maximum ion concentration region that may not coincide with SECL in nanodrops. We compute the ion concentrations in SECL, which are those that should enter the kinetic equation in the ion-evaporation mechanism, instead of the overall drop ion concentration that has been used.
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Affiliation(s)
- Victor Kwan
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7
| | - Styliani Consta
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7
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50
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Yu Y, Liu H, Yu Z, Witkowska HE, Cheng Y. Stoichiometry of Nucleotide Binding to Proteasome AAA+ ATPase Hexamer Established by Native Mass Spectrometry. Mol Cell Proteomics 2020; 19:1997-2015. [PMID: 32883800 PMCID: PMC7710143 DOI: 10.1074/mcp.ra120.002067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 08/04/2020] [Indexed: 11/06/2022] Open
Abstract
AAA+ ATPases constitute a large family of proteins that are involved in a plethora of cellular processes including DNA disassembly, protein degradation and protein complex disassembly. They typically form a hexametric ring-shaped structure with six subunits in a (pseudo) 6-fold symmetry. In a subset of AAA+ ATPases that facilitate protein unfolding and degradation, six subunits cooperate to translocate protein substrates through a central pore in the ring. The number and type of nucleotides in an AAA+ ATPase hexamer is inherently linked to the mechanism that underlies cooperation among subunits and couples ATP hydrolysis with substrate translocation. We conducted a native MS study of a monodispersed form of PAN, an archaeal proteasome AAA+ ATPase, to determine the number of nucleotides bound to each hexamer of the WT protein. We utilized ADP and its analogs (TNP-ADP and mant-ADP), and a nonhydrolyzable ATP analog (AMP-PNP) to study nucleotide site occupancy within the PAN hexamer in ADP- and ATP-binding states, respectively. Throughout all experiments we used a Walker A mutant (PANK217A) that is impaired in nucleotide binding as an internal standard to mitigate the effects of residual solvation on mass measurement accuracy and to serve as a reference protein to control for nonspecific nucleotide binding. This approach led to the unambiguous finding that a WT PAN hexamer carried - from expression host - six tightly bound ADP molecules that could be exchanged for ADP and ATP analogs. Although the Walker A mutant did not bind ADP analogs, it did bind AMP-PNP, albeit at multiple stoichiometries. We observed variable levels of hexamer dissociation and an appearance of multimeric species with the over-charged molecular ion distributions across repeated experiments. We posit that these phenomena originated during ESI process at the final stages of ESI droplet evolution.
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Affiliation(s)
- Yadong Yu
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA
| | - Haichuan Liu
- Department of OBGYN & Reproductive Sci, Sandler-Moore MS Core Facility, University of California San Francisco, San Francisco, California, USA
| | - Zanlin Yu
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA
| | - H Ewa Witkowska
- Department of OBGYN & Reproductive Sci, Sandler-Moore MS Core Facility, University of California San Francisco, San Francisco, California, USA.
| | - Yifan Cheng
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA; Howard Hughes Medical Institute, University of California San Francisco, San Francisco, California, USA.
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