title: Crystal structure of the essential transcription antiterminator M2-1 protein of human respiratory syncytial virus and implications of its phosphorylation.
abstract: The M2-1 protein of the important pathogen human respiratory syncytial virus is a zinc-binding transcription antiterminator that is essential for viral gene expression. We present the crystal structure of full-length M2-1 protein in its native tetrameric form at a resolution of 2.5 Å. The structure reveals that M2-1 forms a disk-like assembly with tetramerization driven by a long helix forming a four-helix bundle at its center, further stabilized by contact between the zinc-binding domain and adjacent protomers. The tetramerization helix is linked to a core domain responsible for RNA binding activity by a flexible region on which lie two functionally critical serine residues that are phosphorylated during infection. The crystal structure of a phosphomimetic M2-1 variant revealed altered charge density surrounding this flexible region although its position was unaffected. Structure-guided mutagenesis identified residues that contributed to RNA binding and antitermination activity, revealing a strong correlation between these two activities, and further defining the role of phosphorylation in M2-1 antitermination activity. The data we present here identify surfaces critical for M2-1 function that may be targeted by antiviral compounds.
authors.affiliation: Astbury Centre for Structural Molecular Biology and School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Sian J
authors.initials: SJ
authors.lastname: Tanner
authors.forename: Antonio
authors.initials: A
authors.lastname: Ariza
authors.forename: Charles-Adrien
authors.initials: CA
authors.lastname: Richard
authors.forename: Hannah F
authors.initials: HF
authors.lastname: Kyle
authors.forename: Rachel L
authors.initials: RL
authors.lastname: Dods
authors.forename: Marie-Lise
authors.initials: ML
authors.lastname: Blondot
authors.forename: Weining
authors.initials: W
authors.lastname: Wu
authors.forename: José
authors.initials: J
authors.lastname: Trincão
authors.forename: Chi H
authors.initials: CH
authors.lastname: Trinh
authors.forename: Julian A
authors.initials: JA
authors.lastname: Hiscox
authors.forename: Miles W
authors.initials: MW
authors.lastname: Carroll
authors.forename: Nigel J
authors.initials: NJ
authors.lastname: Silman
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Eléouët
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Edwards
authors.forename: John N
authors.initials: JN
authors.lastname: Barr
mesh_terms: D001704:Biopolymers / Q000378:metabolism; D018360:Crystallography, X-Ray; D006801:Humans; D019906:Nuclear Magnetic Resonance, Biomolecular; D010766:Phosphorylation; D011487:Protein Conformation; D012313:RNA / Q000378:metabolism; D012136:Respiratory Syncytial Viruses / Q000378:metabolism*; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001704:Biopolymers; D014764:Viral Proteins; D012313:RNA