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Scaffold Properties Are a Key Determinant of the Size and Shape of Self-Assembled Virus-Derived Particles
journal contribution
posted on 2013-12-20, 00:00 authored by Stanislav Kler, Joseph Che-Yen Wang, Mary Dhason, Ariella Oppenheim, Adam ZlotnickControlling the geometry of self-assembly
will enable a greater
diversity of nanoparticles than now available. Viral capsid proteins,
one starting point for investigating self-assembly, have evolved to
form regular particles. The polyomavirus SV40 assembles from pentameric
subunits and can encapsidate anionic cargos. On short ssRNA (≤814
nt), SV40 pentamers form 22 nm diameter capsids. On RNA too long to
fit a T = 1 particle, pentamers forms strings of
22 nm particles and heterogeneous particles of 29–40 nm diameter.
However, on dsDNA SV40 forms 50 nm particles composed of 72 pentamers.
A 7.2-Å resolution cryo-EM image reconstruction of 22 nm particles
shows that they are built of 12 pentamers arranged with T = 1 icosahedral symmetry. At 3-fold vertices, pentamers each contribute
to a three-helix triangle. This geometry of interaction is not seen
in crystal structures of T = 7 viruses and provides
a structural basis for the smaller capsids. We propose that the heterogeneous
particles are actually mosaics formed by combining different geometries
of interaction from T = 1 capsids and virions. Assembly
can be trapped in novel conformations because SV40 interpentamer contacts
are relatively strong. The implication is that by virtue of their
large catalog of interactions, SV40 pentamers have the ability to
self-assemble on and conform to a broad range of shapes.
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22 nm particles12 pentamerspolyomavirus SV 40SV 40 pentamers1 particle7 viruses72 pentamersdsDNA SV 40 forms 50 nm particlesSV 40 interpentamer contactsinteractionRNA1 icosahedral symmetrypentameric subunitsnovel conformationspentamers forms stringsScaffold Propertiescrystal structuresViral capsid proteinsKey Determinant1 capsids
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