title: Self-assembly of heptameric nanoparticles derived from tag-functionalized phi29 connectors.
abstract: The structure of an induced macromolecular assembly was characterized and found to consist of an ordered heptameric arrangement of recombinant phi29 gp10 connector molecules. Insertion of an N-terminal Strep-II/His(6) tag to the connectors led to the spontaneous formation of large nanoparticles that were distinct from free, wild-type phi29 connectors in both size and symmetry elements. The determination of single-molecule tomograms and image-averaged reconstructions allowed for the stoichiometric and topological characterization of the ordered assemblage, revealing that the nanoparticle is composed of five equatorial connectors arranged with pseudo-5-fold rotational symmetry, capped on its ends by two polar connectors. Additionally, all seven connectors are oriented with their narrower N-terminal necks into the nanoparticle core and wider C-terminal ends out toward the nanoparticle surface, a geometric arrangement accommodated by the shape complementarity of the conical connector profiles. A significant amount of conformational heterogeneity was detected, ranging from changes in overall nanoparticle diameter, to tilting of individual connectors, to variations in connector stoichiometry. Nevertheless, a stable, heptameric nanoparticle was resolved, revealing the significant potential of guided, peptide-mediated supramolecular self-assembly. With this construct, we anticipate the further design of variable N-terminal tags to allow for the generation of nanoparticles with tailored connector stoichiometry and topological arrangements. By modifying the surface-exposed C-terminal ends with application-appropriate moieties, the consistent structure and compact nature of these nanoparticles may prove beneficial in nanotechnological and nanomedical approaches.
authors.affiliation: Department of Molecular & Cellular Biology, University of California, Davis, California 95616, USA.
authors.forename: Dominik J
authors.initials: DJ
authors.lastname: Green
authors.forename: Joseph C
authors.initials: JC
authors.lastname: Wang
authors.forename: Feng
authors.initials: F
authors.lastname: Xiao
authors.forename: Ying
authors.initials: Y
authors.lastname: Cai
authors.forename: Rod
authors.initials: R
authors.lastname: Balhorn
authors.forename: Peixuan
authors.initials: P
authors.lastname: Guo
authors.forename: R Holland
authors.initials: RH
authors.lastname: Cheng
mesh_terms: D000595:Amino Acid Sequence; D017103:Bacillus Phages; D006639:Histidine / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D008969:Molecular Sequence Data; D053758:Nanoparticles / Q000737:chemistry*; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism*
chemical_list: D014764:Viral Proteins; D006639:Histidine