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Meier-Credo J, Preiss L, Wüllenweber I, Resemann A, Nordmann C, Zabret J, Suckau D, Michel H, Nowaczyk MM, Meier T, Langer JD. Top-Down Identification and Sequence Analysis of Small Membrane Proteins Using MALDI-MS/MS. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:1293-1302. [PMID: 35758524 PMCID: PMC9264385 DOI: 10.1021/jasms.2c00102] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Identification and sequence determination by mass spectrometry have become routine analyses for soluble proteins. Membrane proteins, however, remain challenging targets due to their hydrophobicity and poor annotation. In particular small membrane proteins often remain unnoticed as they are largely inaccessible to Bottom-Up proteomics. Recent advances in structural biology, though, have led to multiple membrane protein complex structures being determined at sufficiently high resolution to detect uncharacterized, small subunits. In this work we offer a guide for the mass spectrometric characterization of solvent extraction-based purifications of small membrane proteins isolated from protein complexes and cellular membranes. We first demonstrate our Top-Down MALDI-MS/MS approach on a Photosystem II preparation, analyzing target protein masses between 2.5 and 9 kDa with high accuracy and sensitivity. Then we apply our technique to purify and sequence the mycobacterial ATP synthase c subunit, the molecular target of the antibiotic drug bedaquiline. We show that our approach can be used to directly track and pinpoint single amino acid mutations that lead to antibiotic resistance in only 4 h. While not applicable as a high-throughput pipeline, our MALDI-MS/MS and ISD-based approach can identify and provide valuable sequence information on small membrane proteins, which are inaccessible to conventional Bottom-Up techniques. We show that our approach can be used to unambiguously identify single-point mutations leading to antibiotic resistance in mycobacteria.
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Affiliation(s)
- Jakob Meier-Credo
- Proteomics, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
- Proteomics, Max
Planck Institute for Brain Research, Max-von-Laue-Strasse 4, 60438 Frankfurt am Main, Germany
| | - Laura Preiss
- Structural
Biology, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
| | - Imke Wüllenweber
- Proteomics, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
- Proteomics, Max
Planck Institute for Brain Research, Max-von-Laue-Strasse 4, 60438 Frankfurt am Main, Germany
| | - Anja Resemann
- Bruker
Daltonics GmbH & Co. KG, Fahrenheitstrasse 4, 28359 Bremen, Germany
| | - Christoph Nordmann
- Bruker
Daltonics GmbH & Co. KG, Fahrenheitstrasse 4, 28359 Bremen, Germany
| | - Jure Zabret
- Department
of Plant Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany
| | - Detlev Suckau
- Bruker
Daltonics GmbH & Co. KG, Fahrenheitstrasse 4, 28359 Bremen, Germany
| | - Hartmut Michel
- Molecular
Membrane Biology, Max Planck Institute of
Biophysics, Max-von-Laue-Strasse
3, 60438 Frankfurt
am Main, Germany
| | - Marc M. Nowaczyk
- Department
of Plant Biochemistry, Ruhr University Bochum, 44780 Bochum, Germany
| | - Thomas Meier
- Department
of Life Sciences, Imperial College London, Exhibition Road, SW7 2AZ London, United Kingdom
| | - Julian D. Langer
- Proteomics, Max Planck Institute of Biophysics, Max-von-Laue-Strasse 3, 60438 Frankfurt am Main, Germany
- Proteomics, Max
Planck Institute for Brain Research, Max-von-Laue-Strasse 4, 60438 Frankfurt am Main, Germany
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Cohn W, Huguet R, Zabrouskov V, Whitelegge J. Dissociation Strategies to Maximize Coverage of α-Helical Domains in Top-Down Mass Spectrometry of Integral Membrane Proteins. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:1380-1387. [PMID: 33956438 DOI: 10.1021/jasms.1c00031] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Transmembrane α-helical domains of membrane proteins tend to remain structured in the gas phase, presenting a challenge for efficient electron capture/transfer dissociation during top-down dissociation mass spectrometry (MS) experiments. In this study, we compare results from different dissociation modes on a modern Orbitrap platform applied to a model integral membrane protein containing two transmembrane helices, the c-subunit of the Fo domain of the chloroplast ATP synthase. Using commercially available options, we compare collisionally activated dissociation (CAD) with the related variant higher-energy collisional dissociation (HCD) and with electron transfer dissociation (ETD). HCD performed better than CAD and ETD. A combined method utilizing both ETD and HCD (EThcD) demonstrates significant synergy over HCD or ETD alone, representing a robust option analogous to activated ion electron capture dissociation, whereby an infrared laser was used to heat the protein ion alongside electron bombardment. Ultraviolet photodissociation at 213 nm displays at least three backbone dissociation mechanisms and covered nearly 100% of backbone bonds, suggesting significant potential for this technique.
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Affiliation(s)
- Whitaker Cohn
- The Pasarow Mass Spectrometry Laboratory, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California 90024, United States
| | - Romain Huguet
- Thermo Fisher Scientific, San Jose, California 95054, United States
| | - Vlad Zabrouskov
- Thermo Fisher Scientific, San Jose, California 95054, United States
| | - Julian Whitelegge
- The Pasarow Mass Spectrometry Laboratory, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California 90024, United States
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