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Koy C, Röwer C, Thiesen HJ, Neamtu A, Glocker MO. Intact Transition Epitope Mapping-Force Interferences by Variable Extensions (ITEM-FIVE). Biomolecules 2024; 14:454. [PMID: 38672470 PMCID: PMC11048379 DOI: 10.3390/biom14040454] [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: 02/28/2024] [Revised: 03/27/2024] [Accepted: 03/28/2024] [Indexed: 04/28/2024] Open
Abstract
Investigations on binding strength differences of non-covalent protein complex components were performed by mass spectrometry. T4 fibritin foldon (T4Ff) is a well-studied miniprotein, which together with its biotinylated version served as model system to represent a compactly folded protein to which an Intrinsically Disordered Region (IDR) was attached. The apparent enthalpies of the gas phase dissociation reactions of the homo-trimeric foldon F-F-F and of the homo-trimeric triply biotinylated foldon bF-bF-bF have been determined to be rather similar (3.32 kJ/mol and 3.85 kJ/mol) but quite distinct from those of the singly and doubly biotinylated hetero-trimers F-F-bF and F-bF-bF (1.86 kJ/mol and 1.08 kJ/mol). Molecular dynamics simulations suggest that the ground states of the (biotinylated) T4Ff trimers are highly symmetric and well comparable to each other, indicating that the energy levels of all four (biotinylated) T4Ff trimer ground states are nearly indistinguishable. The experimentally determined differences and/or similarities in enthalpies of the complex dissociation reactions are explained by entropic spring effects, which are noticeable in the T4Ff hetero-trimers but not in the T4Ff homo-trimers. A lowering of the transition state energy levels of the T4Ff hetero-trimers seems likely because the biotin moieties, mimicking intrinsically disordered regions (IDRs), induced asymmetries in the transition states of the biotinylated T4Ff hetero-trimers. This transition state energy level lowering effect is absent in the T4Ff homo-trimer, as well as in the triply biotinylated T4Ff homo-trimer. In the latter, the IDR-associated entropic spring effects on complex stability cancel each other out. ITEM-FIVE enabled semi-quantitative determination of energy differences of complex dissociation reactions, whose differences were modulated by IDRs attached to compactly folded proteins.
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Affiliation(s)
- Cornelia Koy
- Proteome Center Rostock, Medical Faculty and Natural Science Faculty, University of Rostock Schillingallee 69, 18057 Rostock, Germany; (C.K.)
| | - Claudia Röwer
- Proteome Center Rostock, Medical Faculty and Natural Science Faculty, University of Rostock Schillingallee 69, 18057 Rostock, Germany; (C.K.)
| | - Hans-Jürgen Thiesen
- Institute for Immunology, Medical Faculty, University of Rostock, Schillingallee 70, 18057 Rostock, Germany;
| | - Andrei Neamtu
- Department of Physiology, “Gr. T. Popa” University of Medicine and Pharmacy, Str. Universitatii nr. 16, 700115 Iasi, Romania
- TRANSCEND Centre, Regional Institute of Oncology (IRO) Iasi, Str. General Henri Mathias Berthelot, Nr. 2–4, 700483 Iasi, Romania
| | - Michael O. Glocker
- Proteome Center Rostock, Medical Faculty and Natural Science Faculty, University of Rostock Schillingallee 69, 18057 Rostock, Germany; (C.K.)
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Röwer C, Olaleye OO, Bischoff R, Glocker MO. Mass Spectrometric ITEM-ONE and ITEM-TWO Analyses Confirm and Refine an Assembled Epitope of an Anti-Pertuzumab Affimer. Biomolecules 2023; 14:24. [PMID: 38254624 PMCID: PMC10813730 DOI: 10.3390/biom14010024] [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: 10/18/2023] [Revised: 12/13/2023] [Accepted: 12/21/2023] [Indexed: 01/24/2024] Open
Abstract
Intact Transition Epitope Mapping-One-step Non-covalent force Exploitation (ITEM-ONE) analysis reveals an assembled epitope on the surface of Pertuzumab, which is recognized by the anti-Pertuzumab affimer 00557_709097. It encompasses amino acid residues NSGGSIYNQRFKGR, which are part of CDR2, as well as residues FTLSVDR, which are located on the variable region of Pertuzumab's heavy chain and together form a surface area of 1381.46 Å2. Despite not being part of Pertuzumab's CDR2, the partial sequence FTLSVDR marks a unique proteotypic Pertuzumab peptide. Binding between intact Pertuzumab and the anti-Pertuzumab affimer was further investigated using the Intact Transition Epitope Mapping-Thermodynamic Weak-force Order (ITEM-TWO) approach. Quantitative analysis of the complex dissociation reaction in the gas phase afforded a quasi-equilibrium constant (KD m0g#) of 3.07 × 10-12. The experimentally determined apparent enthalpy (ΔHm0g#) and apparent free energy (ΔGm0g#) of the complex dissociation reaction indicate that the opposite reaction-complex formation-is spontaneous at room temperature. Due to strong binding to Pertuzumab and because of recognizing Pertuzumab's unique partial amino acid sequences, the anti-Pertuzumab affimer 00557_709097 is considered excellently suitable for implementation in Pertuzumab quantitation assays as well as for the accurate therapeutic drug monitoring of Pertuzumab in biological fluids.
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Affiliation(s)
- Claudia Röwer
- Proteome Center Rostock, Medical Faculty and Natural Science Faculty, University of Rostock, 18057 Rostock, Germany
| | - Oladapo O. Olaleye
- Department of Analytical Biochemistry, Faculty of Science & Engineering, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Rainer Bischoff
- Department of Analytical Biochemistry, Faculty of Science & Engineering, University of Groningen, 9713 AV Groningen, The Netherlands
| | - Michael O. Glocker
- Proteome Center Rostock, Medical Faculty and Natural Science Faculty, University of Rostock, 18057 Rostock, Germany
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Koy C, Glocker UM, Danquah BD, Glocker MO. Native and compactly folded in-solution conformers of pepsin are revealed and distinguished by mass spectrometric ITEM-TWO analyses of gas-phase pepstatin A - pepsin complex binding strength differences. EUROPEAN JOURNAL OF MASS SPECTROMETRY (CHICHESTER, ENGLAND) 2023; 29:303-312. [PMID: 37259551 DOI: 10.1177/14690667231178999] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Pepsin, because of its optimal activity at low acidic pH, has gained importance in mass spectrometric proteome research as a readily available and easy-to-handle protease. Pepsin has also been study object of protein higher-order structure analyses, but questions about how to best investigate pepsin in-solution conformers still remain. We first determined dependencies of pepsin ion charge structures on solvent pH which indicated the in-solution existence of (a) natively folded pepsin (N) which by nanoESI-MS analysis gave rise to a narrow charge state distribution with an 11-fold protonated most intense ion signal, (b) unfolded pepsin (U) with a rather broad ion charge state distribution whose highest ion signal carried 25 protons, and (c) a compactly folded pepsin conformer (C) with a narrow charge structure and a 12-fold protonated ion signal in the center of its charge state envelope. Because pepsin is a protease, unfolded pepsin became its own substrate in solution at pH 6.6 since at this pH some portion of pepsin maintained a compact/native fold which displayed enzymatic activity. Subsequent mass spectrometric ITEM-TWO analyses of pepstatin A - pepsin complex dissociation reactions in the gas phase confirmed a very strong binding of pepstatin A by natively folded pepsin (N). ITEM-TWO further revealed the existence of two compactly folded in-solution pepsin conformers (Ca and Cb) which also were able to bind pepstatin A. Binding strengths of the respective compactly folded pepsin conformer-containing complexes could be determined and apparent gas phase complex dissociation constants and reaction enthalpies differentiated these from each other and from the pepstatin A - pepsin complex which had been formed from natively folded pepsin. Thus, ITEM-TWO turned out to be well suited to pinpoint in-solution pepsin conformers by interrogating quantitative traits of pepstatin A - pepsin complexes in the gas phase.
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Affiliation(s)
- Cornelia Koy
- Proteome Center Rostock, Medical Faculty and Natural Science Faculty, University of Rostock, Rostock, Germany
| | - Ursula M Glocker
- Proteome Center Rostock, Medical Faculty and Natural Science Faculty, University of Rostock, Rostock, Germany
| | - Bright D Danquah
- Proteome Center Rostock, Medical Faculty and Natural Science Faculty, University of Rostock, Rostock, Germany
| | - Michael O Glocker
- Proteome Center Rostock, Medical Faculty and Natural Science Faculty, University of Rostock, Rostock, Germany
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Fischer S, Bürgi J, Gabay-Maskit S, Maier R, Mastalski T, Yifrach E, Obarska-Kosinska A, Rudowitz M, Erdmann R, Platta HW, Wilmanns M, Schuldiner M, Zalckvar E, Oeljeklaus S, Drepper F, Warscheid B. Phosphorylation of the receptor protein Pex5p modulates import of proteins into peroxisomes. Biol Chem 2023; 404:135-155. [PMID: 36122347 PMCID: PMC9929924 DOI: 10.1515/hsz-2022-0168] [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: 04/27/2022] [Accepted: 08/23/2022] [Indexed: 11/15/2022]
Abstract
Peroxisomes are organelles with vital functions in metabolism and their dysfunction is associated with human diseases. To fulfill their multiple roles, peroxisomes import nuclear-encoded matrix proteins, most carrying a peroxisomal targeting signal (PTS) 1. The receptor Pex5p recruits PTS1-proteins for import into peroxisomes; whether and how this process is posttranslationally regulated is unknown. Here, we identify 22 phosphorylation sites of Pex5p. Yeast cells expressing phospho-mimicking Pex5p-S507/523D (Pex5p2D) show decreased import of GFP with a PTS1. We show that the binding affinity between a PTS1-protein and Pex5p2D is reduced. An in vivo analysis of the effect of the phospho-mimicking mutant on PTS1-proteins revealed that import of most, but not all, cargos is affected. The physiological effect of the phosphomimetic mutations correlates with the binding affinity of the corresponding extended PTS1-sequences. Thus, we report a novel Pex5p phosphorylation-dependent mechanism for regulating PTS1-protein import into peroxisomes. In a broader view, this suggests that posttranslational modifications can function in fine-tuning the peroxisomal protein composition and, thus, cellular metabolism.
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Affiliation(s)
- Sven Fischer
- Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, Schänzlestrasse 1, D-79104Freiburg, Germany
| | - Jérôme Bürgi
- Hamburg Unit c/o DESY, European Molecular Biology Laboratory (EMBL), Notkestrasse 85, D-22607Hamburg, Germany
- University Medical Center Hamburg-Eppendorf, Martinistrasse 52, D-20246Hamburg, Germany
| | - Shiran Gabay-Maskit
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot7610001, Israel
| | - Renate Maier
- Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, Schänzlestrasse 1, D-79104Freiburg, Germany
| | - Thomas Mastalski
- Biochemistry of Intracellular Transport, Medical Faculty, Ruhr University Bochum, D-44780Bochum, Germany
| | - Eden Yifrach
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot7610001, Israel
| | - Agnieszka Obarska-Kosinska
- Hamburg Unit c/o DESY, European Molecular Biology Laboratory (EMBL), Notkestrasse 85, D-22607Hamburg, Germany
- University Medical Center Hamburg-Eppendorf, Martinistrasse 52, D-20246Hamburg, Germany
| | - Markus Rudowitz
- Systems Biochemistry, Medical Faculty, Ruhr-University Bochum, D-44780Bochum, Germany
| | - Ralf Erdmann
- Systems Biochemistry, Medical Faculty, Ruhr-University Bochum, D-44780Bochum, Germany
| | - Harald W. Platta
- Biochemistry of Intracellular Transport, Medical Faculty, Ruhr University Bochum, D-44780Bochum, Germany
| | - Matthias Wilmanns
- Hamburg Unit c/o DESY, European Molecular Biology Laboratory (EMBL), Notkestrasse 85, D-22607Hamburg, Germany
- University Medical Center Hamburg-Eppendorf, Martinistrasse 52, D-20246Hamburg, Germany
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot7610001, Israel
| | - Einat Zalckvar
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot7610001, Israel
| | - Silke Oeljeklaus
- Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, Schänzlestrasse 1, D-79104Freiburg, Germany
- Biochemistry II, Theodor Boveri-Institute, Biocenter, University of Würzburg, Am Hubland, D-97074, Würzburg, Germany
| | - Friedel Drepper
- Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, Schänzlestrasse 1, D-79104Freiburg, Germany
| | - Bettina Warscheid
- Biochemistry and Functional Proteomics, Institute of Biology II, Faculty of Biology, University of Freiburg, Schänzlestrasse 1, D-79104Freiburg, Germany
- Biochemistry II, Theodor Boveri-Institute, Biocenter, University of Würzburg, Am Hubland, D-97074, Würzburg, Germany
- Signalling Research Centres BIOSS and CIBSS, University of Freiburg, D-79104Freiburg, Germany
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Scherf M, Koy C, Röwer C, Neamtu A, Glocker MO. Characterization of Phosphorylation-Dependent Antibody Binding to Cancer-Mutated Linkers of C 2H 2 Zinc Finger Proteins by Intact Transition Epitope Mapping-Thermodynamic Weak-Force Order Analysis. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023; 34:171-181. [PMID: 36656134 DOI: 10.1021/jasms.2c00244] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
With Intact Transition Epitope Mapping-Thermodynamic Weak-force Order (ITEM-TWO) analysis in combination with molecular modeling, the phosphorylation-dependent molecular recognition motif of the anti-HpTGEKP antibody has been investigated with binary and ternary component mixtures consisting of antibody and (phospho-) peptides. Amino acid sequences have been selected to match either the antibody's recognition motif or the cancer-related zinc finger protein mutations and phosphorylations of the respective amino acid residues. Upon electrospraying of all the components of the mixtures, that is, hexapeptides, antibody, and intact immune complexes, the produced ions were subjected to mass spectrometric mass filtering. The antibody ions as well as the immune complex ions traversed into the mass spectrometer's collision chamber, whereas paths of unbound peptide ions were blocked prior to entering the collision cell. After dissociation of the multiply charged immune complexes in the gas phase, the complex-released peptide ions were recorded after having traversed the second mass filter. Complex-released peptides were unambiguously identified by their masses using mass analysis with isotope resolution. From the results of our studies with seven (phospho-) peptides with distinct amino acid sequences, which resembled either the antibody's binding motif or mutations, we conclude the following: (i) A negatively charged phospho group, located near the peptide's N-terminus is mandatory for antibody binding when placed on the peptide surface at a precise distance to the C-terminally located positively charged ε-amino group of a lysinyl residue. (ii) A bulky amino acid residue, such as the tyrosinyl residue at the N-terminal position of the (phospho-) threoninyl residue, abolishes antibody binding. (iii) Two closely spaced phospho groups negatively interfere with the surface polarity pattern and abolish antibody binding as well. (iv) Non-phosphorylated peptides are not binding partners of the anti-HpTGEKP antibody.
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Affiliation(s)
- Maximilian Scherf
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Schillingallee 69, 18059 Rostock, Germany
| | - Cornelia Koy
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Schillingallee 69, 18059 Rostock, Germany
| | - Claudia Röwer
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Schillingallee 69, 18059 Rostock, Germany
| | - Andrei Neamtu
- TRANSCEND Centre, Regional Institute of Oncology (IRO) Iasi, Str. General Henri Mathias Berthelot Nr. 2-4, 700483 Iasi, Romania
- Department of Physiology, Grigore T. Popa University of Medicine and Pharmacy of Iasi, Str. Universitatii Nr. 16, 700115 Iasi, Romania
| | - Michael O Glocker
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Schillingallee 69, 18059 Rostock, Germany
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Intact Transition Epitope Mapping-Force Differences between Original and Unusual Residues (ITEM-FOUR). Biomolecules 2023; 13:biom13010187. [PMID: 36671572 PMCID: PMC9856199 DOI: 10.3390/biom13010187] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 01/06/2023] [Accepted: 01/13/2023] [Indexed: 01/19/2023] Open
Abstract
Antibody-based point-of-care diagnostics have become indispensable for modern medicine. In-depth analysis of antibody recognition mechanisms is the key to tailoring the accuracy and precision of test results, which themselves are crucial for targeted and personalized therapy. A rapid and robust method is desired by which binding strengths between antigens and antibodies of concern can be fine-mapped with amino acid residue resolution to examine the assumedly serious effects of single amino acid polymorphisms on insufficiencies of antibody-based detection capabilities of, e.g., life-threatening conditions such as myocardial infarction. The experimental ITEM-FOUR approach makes use of modern mass spectrometry instrumentation to investigate intact immune complexes in the gas phase. ITEM-FOUR together with molecular dynamics simulations, enables the determination of the influences of individually exchanged amino acid residues within a defined epitope on an immune complex's binding strength. Wild-type and mutated epitope peptides were ranked according to their experimentally determined dissociation enthalpies relative to each other, thereby revealing which single amino acid polymorphism caused weakened, impaired, and even abolished antibody binding. Investigating a diagnostically relevant human cardiac Troponin I epitope for which seven nonsynonymous single nucleotide polymorphisms are known to exist in the human population tackles a medically relevant but hitherto unsolved problem of current antibody-based point-of-care diagnostics.
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Koy C, Opuni KFM, Danquah BD, Neamtu A, Glocker MO. Mass Spectrometric and Bio-Computational Binding Strength Analysis of Multiply Charged RNAse S Gas-Phase Complexes Obtained by Electrospray Ionization from Varying In-Solution Equilibrium Conditions. Int J Mol Sci 2021; 22:ijms221910183. [PMID: 34638522 PMCID: PMC8508491 DOI: 10.3390/ijms221910183] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 09/15/2021] [Accepted: 09/17/2021] [Indexed: 11/18/2022] Open
Abstract
We investigated the influence of a solvent’s composition on the stability of desorbed and multiply charged RNAse S ions by analyzing the non-covalent complex’s gas-phase dissociation processes. RNAse S was dissolved in electrospray ionization-compatible buffers with either increasing organic co-solvent content or different pHs. The direct transition of all the ions and the evaporation of the solvent from all the in-solution components of RNAse S under the respective in-solution conditions by electrospray ionization was followed by a collision-induced dissociation of the surviving non-covalent RNAse S complex ions. Both types of changes of solvent conditions yielded in mass spectrometrically observable differences of the in-solution complexation equilibria. Through quantitative analysis of the dissociation products, i.e., from normalized ion abundances of RNAse S, S-protein, and S-peptide, the apparent kinetic and apparent thermodynamic gas-phase complex properties were deduced. From the experimental data, it is concluded that the stability of RNAse S in the gas phase is independent of its in-solution equilibrium but is sensitive to the complexes’ gas-phase charge states. Bio-computational in-silico studies showed that after desolvation and ionization by electrospray, the remaining binding forces kept the S-peptide and S-protein together in the gas phase predominantly by polar interactions, which indirectly stabilized the in-bulk solution predominating non-polar intermolecular interactions. As polar interactions are sensitive to in-solution protonation, bio-computational results provide an explanation of quantitative experimental data with single amino acid residue resolution.
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Affiliation(s)
- Cornelia Koy
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Schillingallee 69, 18057 Rostock, Germany; (C.K.); (K.F.M.O.); (B.D.D.)
| | - Kwabena F. M. Opuni
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Schillingallee 69, 18057 Rostock, Germany; (C.K.); (K.F.M.O.); (B.D.D.)
- Department of Pharmaceutical Chemistry, School of Pharmacy, College of Health Science, University of Ghana, P.O. Box LG43, Legon, Ghana
| | - Bright D. Danquah
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Schillingallee 69, 18057 Rostock, Germany; (C.K.); (K.F.M.O.); (B.D.D.)
| | - Andrei Neamtu
- Department of Physiology, Grigore T. Popa University of Medicine and Pharmacy of Iasi, Str. Universitatii nr. 16, 700051 Iasi, Romania;
| | - Michael O. Glocker
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Schillingallee 69, 18057 Rostock, Germany; (C.K.); (K.F.M.O.); (B.D.D.)
- Correspondence: ; Tel.: +49-381-494-4930; Fax: +49-381-494-4932
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LILBID laser dissociation curves: a mass spectrometry-based method for the quantitative assessment of dsDNA binding affinities. Sci Rep 2020; 10:20398. [PMID: 33230224 PMCID: PMC7683618 DOI: 10.1038/s41598-020-76867-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2020] [Accepted: 10/28/2020] [Indexed: 11/20/2022] Open
Abstract
One current goal in native mass spectrometry is the assignment of binding affinities to noncovalent complexes. Here we introduce a novel implementation of the existing laser-induced liquid bead ion desorption (LILBID) mass spectrometry method: this new method, LILBID laser dissociation curves, assesses binding strengths quantitatively. In all LILBID applications, aqueous sample droplets are irradiated by 3 µm laser pulses. Variation of the laser energy transferred to the droplet during desorption affects the degree of complex dissociation. In LILBID laser dissociation curves, laser energy transfer is purposely varied, and a binding affinity is calculated from the resulting complex dissociation. A series of dsDNAs with different binding affinities was assessed using LILBID laser dissociation curves. The binding affinity results from the LILBID laser dissociation curves strongly correlated with the melting temperatures from UV melting curves and with dissociation constants from isothermal titration calorimetry, standard solution phase methods. LILBID laser dissociation curve data also showed good reproducibility and successfully predicted the melting temperatures and dissociation constants of three DNA sequences. LILBID laser dissociation curves are a promising native mass spectrometry binding affinity method, with reduced time and sample consumption compared to melting curves or titrations.
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Mass Spectrometric Analysis of Antibody-Epitope Peptide Complex Dissociation: Theoretical Concept and Practical Procedure of Binding Strength Characterization. Molecules 2020; 25:molecules25204776. [PMID: 33080923 PMCID: PMC7587528 DOI: 10.3390/molecules25204776] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Revised: 10/09/2020] [Accepted: 10/16/2020] [Indexed: 12/02/2022] Open
Abstract
Electrospray mass spectrometry is applied to determine apparent binding energies and quasi equilibrium dissociation constants of immune complex dissociation reactions in the gas phase. Myoglobin, a natural protein-ligand complex, has been used to develop the procedure which starts from determining mean charge states and normalized and averaged ion intensities. The apparent dissociation constant KD m0g#= 3.60 × 10−12 for the gas phase heme dissociation process was calculated from the mass spectrometry data and by subsequent extrapolation to room temperature to mimic collision conditions for neutral and resting myoglobin. Similarly, for RNAse S dissociation at room temperature a KD m0g#= 4.03 × 10−12 was determined. The protocol was tested with two immune complexes consisting of epitope peptides and monoclonal antibodies. For the epitope peptide dissociation reaction of the FLAG peptide from the antiFLAG antibody complex an apparent gas phase dissociation constant KD m0g#= 4.04 × 10−12 was calculated. Likewise, an apparent KD m0g#= 4.58 × 10−12 was calculated for the troponin I epitope peptide—antiTroponin I antibody immune complex dissociation. Electrospray mass spectrometry is a rapid method, which requires small sample amounts for either identification of protein-bound ligands or for determination of the apparent gas phase protein-ligand complex binding strengths.
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Opuni KFM, Koy C, Russ M, Reepmeyer M, Danquah BD, Weresow M, Alef A, Lorenz P, Thiesen HJ, Glocker MO. ITEM-THREE analysis of a monoclonal anti-malaria antibody reveals its assembled epitope on the pfMSP1 19 antigen. J Biol Chem 2020; 295:14987-14997. [PMID: 32848020 DOI: 10.1074/jbc.ra120.014802] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 08/18/2020] [Indexed: 11/06/2022] Open
Abstract
Rapid diagnostic tests are first-line assays for diagnosing infectious diseases, such as malaria. To minimize false positive and false negative test results in population-screening assays, high-quality reagents and well-characterized antigens and antibodies are needed. An important property of antigen-antibody binding is recognition specificity, which best can be estimated by mapping an antibody's epitope on the respective antigen. We have cloned a malarial antigen-containing fusion protein, MBP-pfMSP119, in Escherichia coli, which then was structurally and functionally characterized before and after high pressure-assisted enzymatic digestion. We then used our previously developed method, intact transition epitope mapping-targeted high-energy rupture of extracted epitopes (ITEM-THREE), to map the area on the MBP-pfMSP119 antigen surface that is recognized by the anti-pfMSP119 antibody G17.12. We identified three epitope-carrying peptides, 386GRNISQHQCVKKQCPQNSGCFRHLDE411, 386GRNISQHQCVKKQCPQNSGCFRHLDEREE414, and 415CKCLLNYKQE424, from the GluC-derived peptide mixture. These peptides belong to an assembled (conformational) epitope on the MBP-pfMSP119 antigen whose identification was substantiated by positive and negative control experiments. In conclusion, our data help to establish a workflow to obtain high-quality control data for diagnostic assays, including the use of ITEM-THREE as a powerful analytical tool. Data are available via ProteomeXchange: PXD019717.
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Affiliation(s)
- Kwabena F M Opuni
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Rostock, Germany; Department of Pharmaceutical Chemistry, School of Pharmacy, College of Health, University of Ghana, Legon, Ghana
| | - Cornelia Koy
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Rostock, Germany
| | - Manuela Russ
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Rostock, Germany
| | - Maren Reepmeyer
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Rostock, Germany
| | - Bright D Danquah
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Rostock, Germany
| | | | | | - Peter Lorenz
- Institute for Immunology, University Medicine Rostock, Rostock, Germany
| | | | - Michael O Glocker
- Proteome Center Rostock, University Medicine Rostock and University of Rostock, Rostock, Germany.
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McAlary L, Harrison JA, Aquilina JA, Fitzgerald SP, Kelso C, Benesch JL, Yerbury JJ. Trajectory Taken by Dimeric Cu/Zn Superoxide Dismutase through the Protein Unfolding and Dissociation Landscape Is Modulated by Salt Bridge Formation. Anal Chem 2019; 92:1702-1711. [DOI: 10.1021/acs.analchem.9b01699] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Luke McAlary
- Illawarra Health and Medical Research Institute, Wollongong, New South Wales 2522, Australia
- Molecular Horizons and School of Chemistry and Molecular Bioscience, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Julian A. Harrison
- Molecular Horizons and School of Chemistry and Molecular Bioscience, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - J. Andrew Aquilina
- Illawarra Health and Medical Research Institute, Wollongong, New South Wales 2522, Australia
- Molecular Horizons and School of Chemistry and Molecular Bioscience, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | | | - Celine Kelso
- Molecular Horizons and School of Chemistry and Molecular Bioscience, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, New South Wales 2522, Australia
| | - Justin L.P. Benesch
- Department of Chemistry, Physical and Theoretical Chemistry Department, University of Oxford, Oxford OX1 3QZ, U.K
| | - Justin J. Yerbury
- Illawarra Health and Medical Research Institute, Wollongong, New South Wales 2522, Australia
- Molecular Horizons and School of Chemistry and Molecular Bioscience, Faculty of Science, Medicine and Health, University of Wollongong, Wollongong, New South Wales 2522, Australia
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Danquah BD, Yefremova Y, Opuni KFM, Röwer C, Koy C, Glocker MO. Intact Transition Epitope Mapping - Thermodynamic Weak-force Order (ITEM - TWO). J Proteomics 2019; 212:103572. [PMID: 31683061 DOI: 10.1016/j.jprot.2019.103572] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Revised: 10/25/2019] [Accepted: 10/27/2019] [Indexed: 01/17/2023]
Abstract
We have developed an electrospray mass spectrometry method which is capable to determine antibody affinity in a gas phase experiment. A solution with the immune complex is electrosprayed and multiply charged ions are translated into the gas phase. Then, the intact immune-complex ions are separated from unbound peptide ions. Increasing the voltage difference in a collision cell results in collision induced dissociation of the immune-complex by which bound peptide ions are released. When analyzing a peptide mixture, measuring the mass of the complex-released peptide ions identifies which of the peptides contains the epitope. A step-wise increase in the collision cell voltage difference changes the intensity ratios of the surviving immune complex ions, the released peptide ions, and the antibody ions. From all the ions´ normalized intensity ratios are deduced the thermodynamic quasi equilibrium dissociation constants (KDm0g#) from which are calculated the apparent gas phase Gibbs energies of activation over temperature (ΔGm0g#T). The order of the apparent gas phase dissociation constants of four antibody - epitope peptide pairs matched well with those obtained from in-solution measurements. The determined gas phase values for antibody affinities are independent from the source of the investigated peptides and from the applied instrument. Data are available via ProteomeXchange with identifier PXD016024. SIGNIFICANCE: ITEM - TWO enables rapid epitope mapping and determination of apparent dissociation energies of immune complexes with minimal in-solution handling. Mixing of antibody and antigen peptide solutions initiates immune complex formation in solution. Epitope binding strengths are determined in the gas phase after electrospraying the antibody / antigen peptide mixtures and mass spectrometric analysis of immune complexes under different collision induced dissociation conditions. Since the order of binding strengths in the gas phase is the same as that in solution, ITEM - TWO characterizes two most important antibody properties, specificity and affinity.
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Affiliation(s)
- Bright D Danquah
- Proteome Center Rostock, University Medicine Rostock, Rostock, Germany
| | - Yelena Yefremova
- Proteome Center Rostock, University Medicine Rostock, Rostock, Germany
| | | | - Claudia Röwer
- Proteome Center Rostock, University Medicine Rostock, Rostock, Germany
| | - Cornelia Koy
- Proteome Center Rostock, University Medicine Rostock, Rostock, Germany
| | - Michael O Glocker
- Proteome Center Rostock, University Medicine Rostock, Rostock, Germany.
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Danquah BD, Röwer C, Opuni KM, El-Kased R, Frommholz D, Illges H, Koy C, Glocker MO. Intact Transition Epitope Mapping - Targeted High-Energy Rupture of Extracted Epitopes (ITEM-THREE). Mol Cell Proteomics 2019; 18:1543-1555. [PMID: 31147491 PMCID: PMC6683010 DOI: 10.1074/mcp.ra119.001429] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Revised: 05/14/2019] [Indexed: 12/31/2022] Open
Abstract
Epitope mapping, which is the identification of antigenic determinants, is essential for the design of novel antibody-based therapeutics and diagnostic tools. ITEM-THREE is a mass spectrometry-based epitope mapping method that can identify epitopes on antigens upon generating an immune complex in electrospray-compatible solutions by adding an antibody of interest to a mixture of peptides from which at least one holds the antibody's epitope. This mixture is nano-electrosprayed without purification. Identification of the epitope peptide is performed within a mass spectrometer that provides an ion mobility cell sandwiched in-between two collision cells and where this ion manipulation setup is flanked by a quadrupole mass analyzer on one side and a time-of-flight mass analyzer on the other side. In a stepwise fashion, immune-complex ions are separated from unbound peptide ions and dissociated to release epitope peptide ions. Immune complex-released peptide ions are separated from antibody ions and fragmented by collision induced dissociation. Epitope-containing peptide fragment ions are recorded, and mass lists are submitted to unsupervised data base search thereby retrieving both, the amino acid sequence of the epitope peptide and the originating antigen. ITEM-THREE was developed with antiTRIM21 and antiRA33 antibodies for which the epitopes were known, subjecting them to mixtures of synthetic peptides of which one contained the respective epitope. ITEM-THREE was then successfully tested with an enzymatic digest of His-tagged recombinant human β-actin and an antiHis-tag antibody, as well as with an enzymatic digest of recombinant human TNFα and an antiTNFα antibody whose epitope was previously unknown.
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Affiliation(s)
- Bright D Danquah
- ‡Proteome Center Rostock, University Medicine Rostock, Rostock, Germany
| | - Claudia Röwer
- ‡Proteome Center Rostock, University Medicine Rostock, Rostock, Germany
| | | | - Reham El-Kased
- ¶Microbiology and Immunology Faculty of Pharmacy, The British University in Egypt, Cairo, Egypt
| | - David Frommholz
- ‖University of Applied Sciences Bonn-Rhein-Sieg, Immunology and Cell Biology, Rheinbach, Germany
| | - Harald Illges
- ‖University of Applied Sciences Bonn-Rhein-Sieg, Immunology and Cell Biology, Rheinbach, Germany;; **University of Applied Sciences Bonn-Rhein-Sieg, Institute for Functional Gene Analytics, Rheinbach, Germany
| | - Cornelia Koy
- ‡Proteome Center Rostock, University Medicine Rostock, Rostock, Germany
| | - Michael O Glocker
- ‡Proteome Center Rostock, University Medicine Rostock, Rostock, Germany.
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Structural Lipids Enable the Formation of Functional Oligomers of the Eukaryotic Purine Symporter UapA. Cell Chem Biol 2018; 25:840-848.e4. [PMID: 29681524 PMCID: PMC6058078 DOI: 10.1016/j.chembiol.2018.03.011] [Citation(s) in RCA: 54] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Revised: 02/27/2018] [Accepted: 03/22/2018] [Indexed: 11/25/2022]
Abstract
The role of membrane lipids in modulating eukaryotic transporter assembly and function remains unclear. We investigated the effect of membrane lipids in the structure and transport activity of the purine transporter UapA from Aspergillus nidulans. We found that UapA exists mainly as a dimer and that two lipid molecules bind per UapA dimer. We identified three phospholipid classes that co-purified with UapA: phosphatidylcholine, phosphatidylethanolamine (PE), and phosphatidylinositol (PI). UapA delipidation caused dissociation of the dimer into monomers. Subsequent addition of PI or PE rescued the UapA dimer and allowed recovery of bound lipids, suggesting a central role of these lipids in stabilizing the dimer. Molecular dynamics simulations predicted a lipid binding site near the UapA dimer interface. Mutational analyses established that lipid binding at this site is essential for formation of functional UapA dimers. We propose that structural lipids have a central role in the formation of functional, dimeric UapA. Mass spectrometry reveals specific lipid binding to the eukaryotic transporter UapA Interfacial lipids stabilize the functional UapA dimer MD simulations reveal the lipid binding sites Mutagenesis of a lipid binding site disrupts UapA dimerization and function in vivo
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