title: The stable association of virion with the triple-gene-block protein 3-based complex of Bamboo mosaic virus.
abstract: The triple-gene-block protein 3 (TGBp3) of Bamboo mosaic virus (BaMV) is an integral endoplasmic reticulum (ER) membrane protein which is assumed to form a membrane complex to deliver the virus intracellularly. However, the virus entity that is delivered to plasmodesmata (PD) and its association with TGBp3-based complexes are not known. Results from chemical extraction and partial proteolysis of TGBp3 in membrane vesicles revealed that TGBp3 has a right-side-out membrane topology; i.e., TGBp3 has its C-terminal tail exposed to the outer surface of ER. Analyses of the TGBp3-specific immunoprecipitate of Sarkosyl-extracted TGBp3-based complex revealed that TGBp1, TGBp2, TGBp3, capsid protein (CP), replicase and viral RNA are potential constituents of virus movement complex. Substantial co-fractionation of TGBp2, TGBp3 and CP, but not TGBp1, in the early eluted gel filtration fractions in which virions were detected after TGBp3-specific immunoprecipitation suggested that the TGBp2- and TGBp3-based complex is able to stably associate with the virion. This notion was confirmed by immunogold-labeling transmission electron microscopy (TEM) of the purified virions. In addition, mutational and confocal microscopy analyses revealed that TGBp3 plays a key role in virus cell-to-cell movement by enhancing the TGBp2- and TGBp3-dependent PD localization of TGBp1. Taken together, our results suggested that the cell-to-cell movement of potexvirus requires stable association of the virion cargo with the TGBp2- and TGBp3-based membrane complex and recruitment of TGBp1 to the PD by this complex.
authors.affiliation: Institute of Biochemistry, National Chung-Hsing University, Taichung, Taiwan, Republic of China.
authors.forename: Yuan-Lin
authors.initials: YL
authors.lastname: Chou
authors.forename: Yi-Jing
authors.initials: YJ
authors.lastname: Hung
authors.forename: Yang-Hao
authors.initials: YH
authors.lastname: Tseng
authors.forename: Hsiu-Ting
authors.initials: HT
authors.lastname: Hsu
authors.forename: Jun-Yi
authors.initials: JY
authors.lastname: Yang
authors.forename: Chiung-Hua
authors.initials: CH
authors.lastname: Wung
authors.forename: Na-Sheng
authors.initials: NS
authors.lastname: Lin
authors.forename: Menghsiao
authors.initials: M
authors.lastname: Meng
authors.forename: Yau-Heiu
authors.initials: YH
authors.lastname: Hsu
authors.forename: Ban-Yang
authors.initials: BY
authors.lastname: Chang
mesh_terms: D017863:Potexvirus / Q000502:physiology*; D017434:Protein Structure, Tertiary; D014026:Nicotiana / Q000166:cytology / Q000235:genetics / Q000378:metabolism / Q000821:virology; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism*; D014771:Virion / Q000235:genetics / Q000378:metabolism*; D019065:Virus Assembly / Q000502:physiology*
chemical_list: D014764:Viral Proteins