| Mud crab (Scylla paramamosain) is an important breed in the coastal areas insoutheast China. One string of reovirus isolated from mud crab (Mud crab reovirus,MCRV) can cause "sleeping disease" in the crabs and result in huge economic loss.In order to better understand MCRV and to seek evidence in preventing andcontrolling the disease, cryo-Electron Microscopy and single particle method wereused to collect data of both full and empty particles of MCRV, and3D reconstructionwas done using EMAN2software package. The results are as follow:1. Structures of full and empty MCRV particles were obtained at4.5and18respectively.3D structure showed that the MCRV capsid consisted of two layers:T=13outer capsid without turret structure and T=2inner capsid.2. In the3D structure of MCRV, the outer capsid is made of spike-likehomo-trimers and hexon center proteins; the inner part consists inner capsid protein intwo conformers A and B, and the transcription complexes including RdRp under the5-fold vertices. Overall, one virus particle contains260copies of outer capsid trimers,120copies of inner capside proteins (60copies of A and B each) and120copies ofhexon center proteins.3. By comparing the structures of the full and empty MCRV particles, we locatedthe transcription complex to be under every5-fold vertex. Moreover, we discoveredfor the first time that after the RNA was released, the inner capsid shifted towards theouter capsid.4. The hexon center protein was identified for the first time, and its structuralarrangement is quite different from the other non-turreted reoviruses, which indicatesits unique role in stablizing the inner and outer capsids.5. Integrating the results from SDS-PAGE analysis and previous studies ofMCRV has lead to speculations of the positions and possible funtions of its structuralproteins.The results above have provided knowledge for further high resolution studies ofstructure and functions of the structural proteins and also vaccine and drug design. |
