title: Determining the topology of virus assembly intermediates using ion mobility spectrometry-mass spectrometry.
abstract: We have combined ion mobility spectrometry-mass spectrometry with tandem mass spectrometry to characterise large, non-covalently bound macromolecular complexes in terms of mass, shape (cross-sectional area) and stability (dissociation) in a single experiment. The results indicate that the quaternary architecture of a complex influences its residual shape following removal of a single subunit by collision-induced dissociation tandem mass spectrometry. Complexes whose subunits are bound to several neighbouring subunits to create a ring-like three-dimensional (3D) architecture undergo significant collapse upon dissociation. In contrast, subunits which have only a single neighbouring subunit within a complex retain much of their original shape upon complex dissociation. Specifically, we have determined the architecture of two transient, on-pathway intermediates observed during in vitro viral capsid assembly. Knowledge of the mass, stoichiometry and cross-sectional area of each viral assembly intermediate allowed us to model a range of potential structures based on the known X-ray structure of the coat protein building blocks. Comparing the cross-sectional areas of these potential architectures before and after dissociation provided tangible evidence for the assignment of the topologies of the complexes, which have been found to encompass both the 3-fold and the 5-fold symmetry axes of the final icosahedral viral shell. Such insights provide unique information about virus assembly pathways that could allow the design of anti-viral therapeutics directed at the assembly step. This methodology can be readily applied to the structural characterisation of many other non-covalently bound macromolecular complexes and their assembly pathways.
authors.affiliation: Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Tom W
authors.initials: TW
authors.lastname: Knapman
authors.affiliation: Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Victoria L
authors.initials: VL
authors.lastname: Morton
authors.affiliation: Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Stonehouse
authors.affiliation: Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Stockley
authors.affiliation: Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Alison E
authors.initials: AE
authors.lastname: Ashcroft
mesh_terms: D000818:Animals; D036022:Capsid Proteins / Q000737:chemistry* / Q000378:metabolism; D002417:Cattle; D018360:Crystallography, X-Ray; D006736:Horses; D006801:Humans; D017909:Levivirus; D008958:Models, Molecular; D008968:Molecular Conformation; D009010:Monte Carlo Method; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000378:metabolism; D055503:Protein Multimerization; D011506:Proteins / Q000737:chemistry / Q000378:metabolism; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D036022:Capsid Proteins; D046912:Multiprotein Complexes; D011506:Proteins