title: Electron microscopic imaging revealed the flexible filamentous structure of the cell attachment protein P2 of Rice dwarf virus located around the icosahedral 5-fold axes.
abstract: The minor outer capsid protein P2 of Rice dwarf virus (RDV), a member of the genus Phytoreovirus in the family Reoviridae, is essential for viral cell entry. Here, we clarified the structure of P2 and the interactions to host insect cells. Negative stain electron microscopy (EM) showed that P2 proteins are monomeric and flexible L-shaped filamentous structures of ∼20 nm in length. Cryo-EM structure revealed the spatial arrangement of P2 in the capsid, which was prescribed by the characteristic virion structure. The P2 proteins were visualized as partial rod-shaped structures of ∼10 nm in length in the cryo-EM map and accommodated in crevasses on the viral surface around icosahedral 5-fold axes with hydrophobic interactions. The remaining disordered region of P2 assumed to be extended to the radial direction towards exterior. Electron tomography clearly showed that RDV particles were away from the cellular membrane at a uniform distance and several spike-like densities, probably corresponding to P2, connecting a viral particle to the host cellular membrane during cell entry. By combining the in vitro and in vivo structural information, we could gain new insights into the detailed mechanism of the cell entry of RDV.
authors.affiliation: Institute for Protein Research, Osaka University, Suita, Osaka, Japan; Supportive Center for Brain Research, National Institute for Physiological Sciences, Okazaki, Aichi, Japan; naomiya@nips.ac.jp.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Miyazaki
authors.affiliation: Institute for Protein Research, Osaka University, Suita, Osaka, Japan;
authors.forename: Akifumi
authors.initials: A
authors.lastname: Higashiura
authors.affiliation: Institute for Protein Research, Osaka University, Suita, Osaka, Japan;
authors.forename: Tomoko
authors.initials: T
authors.lastname: Higashiura
authors.affiliation: Laboratory of Virology, National Agricultural Research Center, Tsukuba, Ibaraki, Japan; and Photosynthesis Research Center, Graduate School of Natural Science and Technology, Okayama University, Okayama, Okayama, Japan.
authors.forename: Fusamichi
authors.initials: F
authors.lastname: Akita
authors.affiliation: Laboratory of Virology, National Agricultural Research Center, Tsukuba, Ibaraki, Japan; and.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hibino
authors.affiliation: Laboratory of Virology, National Agricultural Research Center, Tsukuba, Ibaraki, Japan; and.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Omura
authors.affiliation: Institute for Protein Research, Osaka University, Suita, Osaka, Japan;
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nakagawa
authors.affiliation: Institute for Protein Research, Osaka University, Suita, Osaka, Japan; ikenji@protein.osaka-u.ac.jp.
authors.forename: Kenji
authors.initials: K
authors.lastname: Iwasaki
mesh_terms: D000818:Animals; D002213:Capsid / Q000648:ultrastructure*; D036022:Capsid Proteins / Q000302:isolation & purification / Q000648:ultrastructure*; D002462:Cell Membrane / Q000648:ultrastructure; D002478:Cells, Cultured; D020285:Cryoelectron Microscopy; D055032:Electron Microscope Tomography; D006430:Hemiptera; D012275:Oryza / Q000821:virology*; D012087:Reoviridae / Q000648:ultrastructure*; D014771:Virion / Q000648:ultrastructure; D053586:Virus Internalization
chemical_list: D036022:Capsid Proteins; C108379:protein P2, rice dwarf phytoreovirus
keywords: Phytoreovirus; Rice dwarf virus; cryo-electron microscopy; electron tomography; viral cell entry