title: Reovirus polymerase lambda 3 localized by cryo-electron microscopy of virions at a resolution of 7.6 A.
abstract: Reovirus is an icosahedral, double-stranded (ds) RNA virus that uses viral polymerases packaged within the viral core to transcribe its ten distinct plus-strand RNAs. To localize these polymerases, the structure of the reovirion was refined to a resolution of 7.6 A by cryo-electron microscopy (cryo-EM) and three-dimensional (3D) image reconstruction. X-ray crystal models of reovirus proteins, including polymerase lambda 3, were then fitted into the density map. Each copy of lambda 3 was found anchored to the inner surface of the icosahedral core shell, making major contacts with three molecules of shell protein lambda 1 and overlapping, but not centering on, a five-fold axis. The overlap explains why only one copy of lambda 3 is bound per vertex. lambda 3 is furthermore oriented with its transcript exit channel facing a small channel through the lambda 1 shell, suggesting how the nascent RNA is passed into the large external cavity of the pentameric capping enzyme complex formed by protein lambda 2.
authors: Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA.
authors: Xing
authors: X
authors: Zhang
authors: Stephen B
authors: SB
authors: Walker
authors: Paul R
authors: PR
authors: Chipman
authors: Max L
authors: ML
authors: Nibert
authors: Timothy S
authors: TS
authors: Baker
mesh_terms: D020285:Cryoelectron Microscopy; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry / Q000648:ultrastructure*; D007091:Image Processing, Computer-Assisted; D009690:Nucleic Acid Conformation; D011487:Protein Conformation; D012330:RNA, Double-Stranded / Q000648:ultrastructure*; D012367:RNA, Viral / Q000648:ultrastructure; D012324:RNA-Dependent RNA Polymerase / Q000737:chemistry / Q000648:ultrastructure*; D012087:Reoviridae / Q000201:enzymology* / Q000648:ultrastructure*; D012680:Sensitivity and Specificity; D014764:Viral Proteins / Q000737:chemistry / Q000648:ultrastructure*; D014771:Virion / Q000201:enzymology / Q000648:ultrastructure
chemical_list: D012330:RNA, Double-Stranded; D012367:RNA, Viral; D014764:Viral Proteins; C091731:lambda3 protein, Reovirus; D012324:RNA-Dependent RNA Polymerase; D012321:DNA-Directed RNA Polymerases