title: Structural characterization and oligomerization of PB1-F2, a proapoptotic influenza A virus protein.
abstract: Recently, a novel 87-amino acid influenza A virus protein with proapoptotic properties, PB1-F2, has been reported that originates from an alternative reading frame in the PB1 polymerase gene and is encoded in most known human influenza A virus isolates. Here we characterize the molecular structure of a biologically active synthetic version of the protein (sPB1-F2). Western blot analysis, chemical cross-linking, and NMR spectroscopy afforded direct evidence of the inherent tendency of sPB1-F2 to undergo oligomerization mediated by two distinct domains located in the N and C termini, respectively. CD and (1)H NMR spectroscopic analyses indicate that the stability of structured regions in the molecule clearly depends upon the hydrophobicity of the solvent. In aqueous solutions, the behavior of sPB1-F2 is typical of a largely random coil peptide that, however, adopts alpha-helical structure upon the addition of membrane mimetics. (1)H NMR analysis of three overlapping peptides afforded, for the first time, direct experimental evidence of the presence of a C-terminal region with strong alpha-helical propensity comprising amino acid residues Ile(55)-Lys(85) connected via an essentially random coil structure to a much weaker helix-like region, located in the N terminus between residues Trp(9) and Lys(20). The C-terminal helix is not a true amphipathic helix and is more compact than previously predicted. It corresponds to a positively charged region previously shown to include the mitochondrial targeting sequence of PB1-F2. The consequences of the strong oligomerization and helical propensities of the molecule are discussed and used to formulate a hypothetical model of its interaction with the mitochondrial membrane.
authors.affiliation: Institute of Clinical and Molecular Virology, University of Erlangen-Nürnberg, Erlangen D-91054, Germany.
authors.forename: Karsten
authors.initials: K
authors.lastname: Bruns
authors.forename: Nicole
authors.initials: N
authors.lastname: Studtrucker
authors.forename: Alok
authors.initials: A
authors.lastname: Sharma
authors.forename: Torgils
authors.initials: T
authors.lastname: Fossen
authors.forename: David
authors.initials: D
authors.lastname: Mitzner
authors.forename: André
authors.initials: A
authors.lastname: Eissmann
authors.forename: Uwe
authors.initials: U
authors.lastname: Tessmer
authors.forename: René
authors.initials: R
authors.lastname: Röder
authors.forename: Peter
authors.initials: P
authors.lastname: Henklein
authors.forename: Victor
authors.initials: V
authors.lastname: Wray
authors.forename: Ulrich
authors.initials: U
authors.lastname: Schubert
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D009980:Influenza A virus / Q000378:metabolism*; D008239:Lysine / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012997:Solvents / Q000737:chemistry; D014364:Tryptophan / Q000737:chemistry; D014764:Viral Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: C442816:PB1-F2 protein, Influenza A virus; D012997:Solvents; D014764:Viral Proteins; D014364:Tryptophan; D008239:Lysine