title: Atomic model of a cypovirus built from cryo-EM structure provides insight into the mechanism of mRNA capping.
abstract: The cytoplasmic polyhedrosis virus (CPV) from the family Reoviridae belongs to a subgroup of "turreted" reoviruses, in which the mRNA capping activity occurs in a pentameric turret. We report a full atomic model of CPV built from a 3D density map obtained using cryoelectron microscopy. The image data for the 3D reconstruction were acquired exclusively from a CCD camera. Our structure shows that the enzymatic domains of the pentameric turret of CPV are topologically conserved and that there are five unique channels connecting the guanylyltransferase and methyltransferase regions. This structural organization reveals how the channels guide nascent mRNA sequentially to guanylyltransferase, 7-N-methyltransferase, and 2'-O-methyltransferase in the turret, undergoing the highly coordinated mRNA capping activity. Furthermore, by fitting the deduced amino acid sequence of the protein VP5 to 120 large protrusion proteins on the CPV capsid shell, we confirmed that this protrusion protein is encoded by CPV RNA segment 7.
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China.
authors.forename: Lingpeng
authors.initials: L
authors.lastname: Cheng
authors.forename: Jingchen
authors.initials: J
authors.lastname: Sun
authors.forename: Kai
authors.initials: K
authors.lastname: Zhang
authors.forename: Zongjun
authors.initials: Z
authors.lastname: Mou
authors.forename: Xiaoxing
authors.initials: X
authors.lastname: Huang
authors.forename: Gang
authors.initials: G
authors.lastname: Ji
authors.forename: Fei
authors.initials: F
authors.lastname: Sun
authors.forename: Jingqiang
authors.initials: J
authors.lastname: Zhang
authors.forename: Ping
authors.initials: P
authors.lastname: Zhu
mesh_terms: D000595:Amino Acid Sequence; D002213:Capsid / Q000378:metabolism / Q000648:ultrastructure*; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics / Q000648:ultrastructure; D020285:Cryoelectron Microscopy / Q000379:methods*; D008958:Models, Molecular; D008961:Models, Structural; D008969:Molecular Sequence Data; D015394:Molecular Structure; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012315:RNA Caps; D012333:RNA, Messenger / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D012087:Reoviridae / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure*; D017386:Sequence Homology, Amino Acid
chemical_list: D036022:Capsid Proteins; D012315:RNA Caps; D012333:RNA, Messenger; D012367:RNA, Viral