Kevin Jeanne Dit Fouque1, Hélène Lavanant1, Séverine Zirah2, Jérôme Lemoine3, Sylvie Rebuffat2, Jean-Claude Tabet4, Alexander Kulesza5, Carlos Afonso1, Philippe Dugourd5, Fabien Chirot3. 1. Normandie Université, COBRA, UMR 6014 and FR 3038, Université de Rouen; INSA Rouen; CNRS, IRCOF, 1 Rue Tesnière, 76821, Mont-Saint-Aignan Cedex, France. 2. Molécules de Communication et Adaptation des Microorganismes (MCAM, UMR 7245), Sorbonne Universités, Muséum national d'Histoire naturelle, CNRS, CP 54, 57 rue Cuvier, 75005, Paris, France. 3. Université de Lyon, Université Lyon 1, ENS Lyon, CNRS UMR5280, ISA, 5 rue de la Doua, 69100, Villeurbanne, France. 4. Institut Parisien de Chimie Moléculaire, UMR 7201, CNRS, Université Pierre et Marie Curie, 4 place Jussieu, 75005, Paris, France. 5. Université de Lyon, Université Lyon 1, CNRS UMR5306, ILM, 5 rue de la Doua, 69100, Villeurbanne, France.
Abstract
RATIONALE: Capistruin is a peptide synthesized by Burkholderia thailandensis E264, which displays a lasso topology. This knot-like structure confers interesting properties to peptides (e.g. antibacterial). Therefore, it is important to evaluate the sensitivity of structural characterization methods to such topological constraints. METHODS: Ion mobility mass spectrometry (IMS-MS) experiments, using both drift tube and travelling wave instruments, were performed on lasso capistruin and on peptides with the same sequence, but displaying a branched-cyclic (un-threaded) or linear topology. Molecular dynamics (MD) simulations were then performed to further interpret the IMS results in terms of conformation. RESULTS: The collision cross sections (CCSs) measured via IMS for the different forms of capistruin were found to be similar, despite their different topologies for the doubly charged species, but significant differences arise as the charge state is increased. MD simulations for the doubly charged linear peptide were consistent with the hypothesis that salt bridges are present in the gas phase. Moreover, through CCS measurements for peptides with site-specific mutations, the arginine residue at position 11 was found to play a major role in the stabilization of compact structures for the linear peptide. CONCLUSIONS: Differences in peptide topologies did not yield marked signatures in their respective IMS spectra. Such signatures were only visible for relatively high charge states, that allow Coulomb repulsion to force unfolding. At low charge states, the topologically unconstrained linear form of capistruin was found to adopt charge solvation-constrained structures, possibly including salt bridges, with CCSs comparable to those measured for the topologically constrained lasso form.
RATIONALE: Capistruin is a peptide synthesized by Burkholderia thailandensis E264, which displays a lasso topology. This knot-like structure confers interesting properties to peptides (e.g. antibacterial). Therefore, it is important to evaluate the sensitivity of structural characterization methods to such topological constraints. METHODS: Ion mobility mass spectrometry (IMS-MS) experiments, using both drift tube and travelling wave instruments, were performed on lasso capistruin and on peptides with the same sequence, but displaying a branched-cyclic (un-threaded) or linear topology. Molecular dynamics (MD) simulations were then performed to further interpret the IMS results in terms of conformation. RESULTS: The collision cross sections (CCSs) measured via IMS for the different forms of capistruin were found to be similar, despite their different topologies for the doubly charged species, but significant differences arise as the charge state is increased. MD simulations for the doubly charged linear peptide were consistent with the hypothesis that salt bridges are present in the gas phase. Moreover, through CCS measurements for peptides with site-specific mutations, the arginine residue at position 11 was found to play a major role in the stabilization of compact structures for the linear peptide. CONCLUSIONS: Differences in peptide topologies did not yield marked signatures in their respective IMS spectra. Such signatures were only visible for relatively high charge states, that allow Coulomb repulsion to force unfolding. At low charge states, the topologically unconstrained linear form of capistruin was found to adopt charge solvation-constrained structures, possibly including salt bridges, with CCSs comparable to those measured for the topologically constrained lasso form.
Authors: Kevin Jeanne Dit Fouque; Hélène Lavanant; Séverine Zirah; Julian D Hegemann; Marcel Zimmermann; Mohamed A Marahiel; Sylvie Rebuffat; Carlos Afonso Journal: J Am Soc Mass Spectrom Date: 2016-11-03 Impact factor: 3.109