title: Crystal structure of the superfamily 1 helicase from Tomato mosaic virus.
abstract: The genomes of the Tomato mosaic virus and many other plant and animal positive-strand RNA viruses of agronomic and medical importance encode superfamily 1 helicases. Although helicases play important roles in viral replication, the crystal structures of viral superfamily 1 helicases have not been determined. Here, we report the crystal structure of a fragment (S666 to Q1116) of the replication protein from Tomato mosaic virus. The structure reveals a novel N-terminal domain tightly associated with a helicase core. The helicase core contains two RecA-like α/β domains without any of the accessory domain insertions that are found in other superfamily 1 helicases. The N-terminal domain contains a flexible loop, a long α-helix, and an antiparallel six-stranded β-sheet. On the basis of the structure, we constructed deletion mutants of the S666-to-Q1116 fragment and performed split-ubiquitin-based interaction assays in Saccharomyces cerevisiae with TOM1 and ARL8, host proteins that are essential for tomato mosaic virus RNA replication. The results suggested that both TOM1 and ARL8 interact with the long α-helix in the N-terminal domain and that TOM1 also interacts with the helicase core. Prediction of secondary structures in other viral superfamily 1 helicases and comparison of those structures with the S666-to-Q1116 structure suggested that these helicases have a similar fold. Our results provide a structural basis of viral superfamily 1 helicases.
authors.affiliation: Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Nishikiori
authors.forename: Shigeru
authors.initials: S
authors.lastname: Sugiyama
authors.forename: Hongyu
authors.initials: H
authors.lastname: Xiang
authors.forename: Mayumi
authors.initials: M
authors.lastname: Niiyama
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Ishibashi
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Inoue
authors.forename: Masayuki
authors.initials: M
authors.lastname: Ishikawa
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Matsumura
authors.forename: Etsuko
authors.initials: E
authors.lastname: Katoh
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D020558:GTP Phosphohydrolases / Q000737:chemistry; D008958:Models, Molecular; D009154:Mutation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D020365:RNA Helicases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000821:virology; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism; D016415:Sequence Alignment; D017384:Sequence Deletion; D017898:Tobamovirus / Q000201:enzymology*; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000378:metabolism
chemical_list: D029701:Saccharomyces cerevisiae Proteins; C115246:TOM1 protein, S cerevisiae; D044767:Ubiquitin-Protein Ligases; D020558:GTP Phosphohydrolases; D020365:RNA Helicases