title: Three-dimensional structure and function of the Paramecium bursaria chlorella virus capsid.
abstract: A cryoelectron microscopy 8.5 Å resolution map of the 1,900 Å diameter, icosahedral, internally enveloped Paramecium bursaria chlorella virus was used to interpret structures of the virus at initial stages of cell infection. A fivefold averaged map demonstrated that two minor capsid proteins involved in stabilizing the capsid are missing in the vicinity of the unique vertex. Reconstruction of the virus in the presence of host chlorella cell walls established that the spike at the unique vertex initiates binding to the cell wall, which results in the enveloped nucleocapsid moving closer to the cell. This process is concurrent with the release of the internal viral membrane that was linked to the capsid by many copies of a viral membrane protein in the mature infectous virus. Simultaneously, part of the trisymmetrons around the unique vertex disassemble, probably in part because two minor capsid proteins are absent, causing Paramecium bursaria chlorella virus and the cellular contents to merge, possibly as a result of enzyme(s) within the spike assembly. This may be one of only a few recordings of successive stages of a virus while infecting a eukaryotic host in pseudoatomic detail in three dimensions.
authors.affiliation: Department of Biological Sciences, Purdue University, 240 South Martin Jischke Drive, West Lafayette, IN 47907-2032, USA.
authors.forename: Xinzheng
authors.initials: X
authors.lastname: Zhang
authors.forename: Ye
authors.initials: Y
authors.lastname: Xiang
authors.forename: David D
authors.initials: DD
authors.lastname: Dunigan
authors.forename: Thomas
authors.initials: T
authors.lastname: Klose
authors.forename: Paul R
authors.initials: PR
authors.lastname: Chipman
authors.forename: James L
authors.initials: JL
authors.lastname: Van Etten
authors.forename: Michael G
authors.initials: MG
authors.lastname: Rossmann
mesh_terms: D002213:Capsid / Q000737:chemistry* / Q000378:metabolism; D002708:Chlorella / Q000821:virology; D017862:Phycodnaviridae / Q000737:chemistry* / Q000502:physiology; D020836:Protein Structure, Quaternary; D014764:Viral Proteins / Q000737:chemistry*; D019065:Virus Assembly / Q000502:physiology; D057074:Virus Release / Q000502:physiology
chemical_list: D014764:Viral Proteins