title: Crystal structure of the polymerase PA(C)-PB1(N) complex from an avian influenza H5N1 virus.
abstract: The recent emergence of highly pathogenic avian influenza A virus strains with subtype H5N1 pose a global threat to human health. Elucidation of the underlying mechanisms of viral replication is critical for development of anti-influenza virus drugs. The influenza RNA-dependent RNA polymerase (RdRp) heterotrimer has crucial roles in viral RNA replication and transcription. It contains three proteins: PA, PB1 and PB2. PB1 harbours polymerase and endonuclease activities and PB2 is responsible for cap binding; PA is implicated in RNA replication and proteolytic activity, although its function is less clearly defined. Here we report the 2.9 ångström structure of avian H5N1 influenza A virus PA (PA(C), residues 257-716) in complex with the PA-binding region of PB1 (PB1(N), residues 1-25). PA(C) has a fold resembling a dragon's head with PB1(N) clamped into its open 'jaws'. PB1(N) is a known inhibitor that blocks assembly of the polymerase heterotrimer and abolishes viral replication. Our structure provides details for the binding of PB1(N) to PA(C) at the atomic level, demonstrating a potential target for novel anti-influenza therapeutics. We also discuss a potential nucleotide binding site and the roles of some known residues involved in polymerase activity. Furthermore, to explore the role of PA in viral replication and transcription, we propose a model for the influenza RdRp heterotrimer by comparing PA(C) with the lambda3 reovirus polymerase structure, and docking the PA(C) structure into an available low resolution electron microscopy map.
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Xiaojing
authors.initials: X
authors.lastname: He
authors.forename: Jie
authors.initials: J
authors.lastname: Zhou
authors.forename: Mark
authors.initials: M
authors.lastname: Bartlam
authors.forename: Rongguang
authors.initials: R
authors.lastname: Zhang
authors.forename: Jianyuan
authors.initials: J
authors.lastname: Ma
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Lou
authors.forename: Xuemei
authors.initials: X
authors.lastname: Li
authors.forename: Jingjing
authors.initials: J
authors.lastname: Li
authors.forename: Andrzej
authors.initials: A
authors.lastname: Joachimiak
authors.forename: Zonghao
authors.initials: Z
authors.lastname: Zeng
authors.forename: Ruowen
authors.initials: R
authors.lastname: Ge
authors.forename: Zihe
authors.initials: Z
authors.lastname: Rao
authors.forename: Yingfang
authors.initials: Y
authors.lastname: Liu
mesh_terms: D000818:Animals; D001665:Binding Sites; D001717:Birds / Q000821:virology*; D018360:Crystallography, X-Ray; D053124:Influenza A Virus, H5N1 Subtype / Q000201:enzymology*; D008958:Models, Molecular; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism; D009711:Nucleotides / Q000378:metabolism; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D012324:RNA-Dependent RNA Polymerase / Q000737:chemistry* / Q000378:metabolism; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism*; D014779:Virus Replication
chemical_list: D009097:Multienzyme Complexes; D009711:Nucleotides; C061290:PA protein, influenza viruses; D010446:Peptide Fragments; D014764:Viral Proteins; C077346:influenza virus polymerase basic protein 1; D012324:RNA-Dependent RNA Polymerase