Identification of the Cap-binding Protein of Two Strains of Influenza A/FPV

We have identified the cap-recognizing protein of two strains of influenza A fowl plague virus (FPV) by photoaffinity labelling of virion proteins with a photoreactive analogue of the 5′-methyl cap structure of messenger RNA. The cap-recognizing protein of influenza A/FPV/Rostock/34 is the P2 polypeptide, and that of influenza A/FPV/Dutch/27 (Dobson) is the P3 polypeptide. In each case the cap-recognizing protein is the product of RNA segment 1.