title: Backbone model of an aquareovirus virion by cryo-electron microscopy and bioinformatics.
abstract: Grass carp reovirus (GCRV) is a member of the aquareovirus genus in the Reoviridae family and has a capsid with two shells-a transcription-competent core surrounded by a coat. We report a near-atomic-resolution reconstruction of the GCRV virion by cryo-electron microscopy and single-particle reconstruction. A backbone model of the GCRV virion, including seven conformers of the five capsid proteins making up the 1500 molecules in both the core and the coat, was derived using cryo-electron microscopy density-map-constrained homology modeling and refinement. Our structure clearly showed that the amino-terminal segment of core protein VP3B forms an approximately 120-A-long alpha-helix-rich extension bridging across the icosahedral 2-fold-symmetry-related molecular interface. The presence of this unique structure across this interface and the lack of an external cementing molecule at this location in GCRV suggest a stabilizing role of this extended amino-terminal density. Moreover, part of this amino-terminal extension becomes invisible in the reconstruction of transcription-competent core particles, suggesting its involvement in endogenous viral RNA transcription. Our structure of the VP1 turret represents its open state, and comparison with its related structures at the closed state suggests hinge-like domain movements associated with the mRNA-capping machinery. Overall, this first backbone model of an aquareovirus virion provides a wealth of structural information for understanding the structural basis of GCRV assembly and transcription.
authors.affiliation: Department of Microbiology, Immunology and Molecular Genetics, University of California at Los Angeles, Los Angeles, CA 90095-7364, USA.
authors.forename: Lingpeng
authors.initials: L
authors.lastname: Cheng
authors.forename: Jiang
authors.initials: J
authors.lastname: Zhu
authors.forename: Wong Hoi
authors.initials: WH
authors.lastname: Hui
authors.forename: Xiaokang
authors.initials: X
authors.lastname: Zhang
authors.forename: Barry
authors.initials: B
authors.lastname: Honig
authors.forename: Qin
authors.initials: Q
authors.lastname: Fang
authors.forename: Z Hong
authors.initials: ZH
authors.lastname: Zhou
mesh_terms: D000818:Animals; D002347:Carps / Q000821:virology*; D019295:Computational Biology; D020285:Cryoelectron Microscopy; D008958:Models, Molecular; D011487:Protein Conformation; D012087:Reoviridae / Q000737:chemistry / Q000648:ultrastructure*; D014764:Viral Proteins / Q000737:chemistry* / Q000648:ultrastructure; D014771:Virion / Q000648:ultrastructure*
chemical_list: D014764:Viral Proteins