Three-Dimensional Reconstruction of Icosahedral Virus by Symmetry-Adapted Functions

A three-dimensional （3D） reconstruction of icosahedral virus is carried out by the icosahedral symmetry-adapted function （ISAF） method in spherical coordinates. In order to reduce the influence of noise, it is better to use the basis functions that have identical symmetry with the object reconstructed. It is verified that the ISAF method has stronger ability to reduce the influence of noise to grain the resolution better than that of the conventional method by the simulation of 3D reconstruction.

3D reconstruction and capsid protein characterization of grass carp reovirus

Grass carp reovirus (GCRV) is a relatively new virus first isolated in China and is a member of the Aquareovirus genus of the Reoviridae family. Recent report of genomic se-quencing showed that GCRV shared high degree of homology with mammalian reovirus (MRV). As a step of our effort to understand the structural basis of GCRV pathogenesis, we determined the three-dimensional (3D) structure of GCRV capsid at 17 ? resolution by electron cryomicro-scopy. Each GCRV capsid has a multilayered organization, consisting of an RNA core, an inner, middle and outer protein layer. The outer layer is made up of 200 trimers that are arranged on an incomplete T=13 icosahedral lattice. A characteristic feature of this layer is the depression re-sulting from the absence of trimers around the peripentonal positions, revealing the underlying trimers on the middle layer. There are 120 subunits in the inner layer arranged with T=1 symme-try. These structural features are common to other members of the Reoviridae. Moreover, SDS-PAGE analysis showed that GCRV virions contain seven structural proteins (VP1-VP7). These structural proteins have a high degree of sequence homology to MRV, consistent with the structural similarities observed in our study. The high structural similarities of isolated GCRV and MRV suggest that future structural studies focusing on GCRV entering into and replicating within its host cell are necessary in order to fully understand the structural basis of GCRV pathogenesis.

Three-dimensional structure determination of capsid of Aedes albopicus C6/36 cell densovirus

The three-dimensional structure of capsid of Aedes albopictus C6/36 densovirus was determined to 14- resolution by electron cryomicroscopy and computer reconstruction. The triangulation number of the capsid is 1. There are 12 holes in each triangular face and a spike on each 5-fold vertex. The validity of the capsid and nucleic acid densities in the reconstructions was discussed.

Three-dimensional structure of the wild-type RHDV

The three-dimensional (3D) structure of the wild-type rabbit hemorrhagic disease virus (RHDV) has been determined to a resolution of 3.2 nm by electron cryo-microscopy and computer image reconstruction techniques. The 3D density map exhibits characteristic structural features of a calicivirus: a T=3 icosahedral capsid with 90 arch-like capsomeres at the icosahedral and local 2-fold axes and 32 large surface hollows at the icosahedral 5- and 3-fold axes. This result confirms that the RHDV isolated in China is a member of the Caliciviridae family. A rather continuous capsid shell was found without channels. However, our RHDV structure also reveals some distinct structural char-acteristics not observed in other caliciviruses, including interconnected capsomeres and the lack of protuberance on the base of each of the surface hollows. Two types of particles were identified with similar outer capsid structure but different density distributions inside the capsid shells, which could not be distinguished by