title: Engineering thermal stability in RNA phage capsids via disulphide bonds.
abstract: The RNA bacteriophages, a group that includes phages Qbeta and MS2, have a number of potential bionanotechnological applications, including cell specific drug delivery and as substrates for the formation of novel materials. Despite extensive sequence identity between their coat protein subunits, and an almost identical three-dimensional fold, Qbeta and MS2 capsids have dramatically different thermal stabilities. The increased stability of Qbeta has been correlated with the inter-subunit disulphide bonds present in that capsid and not present in MS2. We have tested this hypothesis directly using mass spectrometry. Analysis of the dissociated coat protein subunits suggests that inter-molecular disulphides are formed at the capsid five-fold but may not be at the three-fold axes. This conclusion has been tested by engineering disulphide cross-links into either the five-fold or three-fold positions of the recombinant MS2 capsid. Five-fold cross-linking results in a mutant with stability properties similar to those of Qbeta. Three-fold cross-linking results in a mutant unable to assemble T = 3 shells, implying that five-fold structures are on pathway to capsid assembly in these phages. The results demonstrate how it is possible to redesign the physical properties of phage shells and may be of general relevance to future applications of viruses and virus-like particles.
authors.affiliation: Astbury Centre for Structural Molecular Biology, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Alison E
authors.initials: AE
authors.lastname: Ashcroft
authors.forename: Hugo
authors.initials: H
authors.lastname: Lago
authors.forename: Jacyara M B
authors.initials: JM
authors.lastname: Macedo
authors.forename: Wilf T
authors.initials: WT
authors.lastname: Horn
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Stonehouse
authors.forename: Peter G
authors.initials: PG
authors.lastname: Stockley
mesh_terms: D017908:Allolevivirus / Q000737:chemistry*; D000595:Amino Acid Sequence; D002213:Capsid / Q000737:chemistry*; D004220:Disulfides / Q000737:chemistry*; D017909:Levivirus / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D036103:Nanotechnology; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics
chemical_list: D004220:Disulfides; D014764:Viral Proteins