title: New antiviral target revealed by the hexameric structure of mouse hepatitis virus nonstructural protein nsp15.
abstract: The unique coronavirus transcription/replication machinery comprised of multiple virus-encoded nonstructural proteins (nsp) plays a vital role during initial and intermediate phases of the viral life cycle. The crystal structure of mouse hepatitis virus strain A59 (MHV-A59) nsp15 is reported at 2.15-A resolution. nsp15 is an XendoU endoribonuclease and is the first one from this family to have its structure unveiled. The MHV-A59 nsp15 monomer structure has a novel protein fold. Two nsp15 trimers form a back-to-back hexamer that is believed to be the functional unit. The structure reveals the catalytic site including the highly conserved residues His262, His277, and Lys317, which is supported by mutagenesis analysis. Gel filtration and enzyme activity assays confirmed that the hexamer is the active form for nsp15 and demonstrate the specificity of nsp15 for uridylate. The high sequence conservation of nsp15 in coronaviruses, including that of severe acute respiratory syndrome, suggests that this protein may provide a new target for the design of antiviral therapeutics.
authors.affiliation: Tsinghua-IBP Joint Research Group for Structural Biology, Tsinghua University, Beijing 100084, China.
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Xu
authors.forename: Yujia
authors.initials: Y
authors.lastname: Zhai
authors.forename: Fei
authors.initials: F
authors.lastname: Sun
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Lou
authors.forename: Dan
authors.initials: D
authors.lastname: Su
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Xu
authors.forename: Rongguang
authors.initials: R
authors.lastname: Zhang
authors.forename: Andrzej
authors.initials: A
authors.lastname: Joachimiak
authors.forename: Xuejun C
authors.initials: XC
authors.lastname: Zhang
authors.forename: Mark
authors.initials: M
authors.lastname: Bartlam
authors.forename: Zihe
authors.initials: Z
authors.lastname: Rao
mesh_terms: D000595:Amino Acid Sequence; D000998:Antiviral Agents / Q000737:chemistry; D020134:Catalytic Domain; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D015195:Drug Design; D004722:Endoribonucleases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008345:Manganese / Q000737:chemistry; D008969:Molecular Sequence Data; D006517:Murine hepatitis virus / Q000378:metabolism*; D016296:Mutagenesis; D009154:Mutation; D011487:Protein Conformation; D017510:Protein Folding; D017361:Viral Nonstructural Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D000998:Antiviral Agents; D017361:Viral Nonstructural Proteins; D008345:Manganese; D004722:Endoribonucleases