Structure and Nuclear Import Function of the C-terminal Domain of Influenza Virus Polymerase PB2 Subunit

Nat Struct Mol Biol. 2007 Mar;14(3):229-33. doi: 10.1038/nsmb1212. Epub 2007 Feb 25.


The trimeric influenza virus polymerase, comprising subunits PA, PB1 and PB2, is responsible for transcription and replication of the segmented viral RNA genome. Using a novel library-based screening technique called expression of soluble proteins by random incremental truncation (ESPRIT), we identified an independently folded C-terminal domain from PB2 and determined its solution structure by NMR. Using green fluorescent protein fusions, we show that both the domain and the full-length PB2 subunit are efficiently imported into the nucleus dependent on a previously overlooked bipartite nuclear localization sequence (NLS). The crystal structure of the domain complexed with human importin alpha5 shows how the last 20 residues unfold to permit binding to the import factor. The domain contains three surface residues implicated in adaptation from avian to mammalian hosts. One of these tethers the NLS-containing peptide to the core of the domain in the unbound state.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Active Transport, Cell Nucleus*
  • Amino Acid Sequence
  • Cell Nucleus / metabolism*
  • Cell Survival
  • Crystallography, X-Ray
  • Humans
  • Magnetic Resonance Spectroscopy
  • Molecular Sequence Data
  • Nuclear Localization Signals
  • Orthomyxoviridae / enzymology*
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Protein Subunits / chemistry*
  • Protein Subunits / metabolism*
  • Solubility
  • Solutions
  • Viral Proteins / chemistry*
  • Viral Proteins / metabolism*
  • alpha Karyopherins / chemistry


  • KPNA1 protein, human
  • Nuclear Localization Signals
  • PB2 protein, influenza virus
  • Protein Subunits
  • Solutions
  • Viral Proteins
  • alpha Karyopherins

Associated data

  • PDB/2GMO
  • PDB/2JDQ