Dissecting the Dynamic Conformations of the Metamorphic Protein Lymphotactin
| Autor: | Sophie R. Harvey, Cait E. MacPhee, Robert C. Tyler, Patrick R. R. Langridge-Smith, Albert Konijnenberg, Massimiliano Porrini, Perdita E. Barran, Brian F. Volkman, David Clarke |
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| Rok vydání: | 2014 |
| Předmět: |
Sialoglycoproteins
Dimer Molecular Dynamics Simulation Intrinsically disordered proteins Mass Spectrometry Protein Structure Secondary chemistry.chemical_compound Molecular dynamics Fragmentation (mass spectrometry) Materials Chemistry Native state Humans Disulfides Physical and Theoretical Chemistry Conformational isomerism Lymphokines Electron-capture dissociation Protein Stability Hydrogen Bonding Peptide Fragments Surfaces Coatings and Films Crystallography Monomer chemistry Gases Protein Multimerization |
| Zdroj: | The Journal of Physical Chemistry B. 118:12348-12359 |
| ISSN: | 1520-5207 1520-6106 |
| Popis: | A mass spectrometer provides an ideal laboratory to probe the structure and stability of isolated protein ions. Interrogation of each discrete mass/charge-separated species enables the determination of the intrinsic stability of a protein fold, gaining snapshots of unfolding pathways. In solution, the metamorphic protein lymphotactin (Ltn) exists in equilibrium between two distinct conformations, a monomeric (Ltn10) and a dimeric (Ltn40) fold. Here, we use electron capture dissociation (ECD) and drift tube ion mobility-mass spectrometry (DT IM-MS) to analyze both forms and use molecular dynamics (MD) to consider how the solution fold alters in a solvent-free environment. DT IM-MS reveals significant conformational flexibility for the monomer, while the dimer appears more conformationally restricted. These findings are supported by MD calculations, which reveal how salt bridges stabilize the conformers in vacuo. Following ECD experiments, a distinctive fragmentation pattern is obtained for both the monomer and dimer. Monomer fragmentation becomes more pronounced with increasing charge state especially in the disordered regions and C-terminal α-helix in the solution fold. Lower levels of fragmentation are seen in the β-sheet regions and in regions that contain salt bridges, identified by MD simulations. The lowest charge state of the dimer for which we obtain ECD data ([D+9H](9+)) exhibits extensive fragmentation with no relationship to the solution fold and has a smaller collision cross section (CCS) than charge states 10-13+, suggesting a "collapsed" encounter complex. Other charge states of the dimer, as for the monomer, are resistant to fragmentation in regions of β-sheets in the solution fold. This study provides evidence for preservation and loss of global fold and secondary structural elements, providing a tantalizing glimpse into the power of the emerging field of native top-down mass spectrometry. |
| Databáze: | OpenAIRE |
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