The structural polypeptides of fowl plague virus (influenza A) and those synthesized in fowl plague virus-infected chick embryo fibroblasts have been analyzed by high resolution polyacrylamide gel electrophoresis. We detected eight distinct virus gene products: three polymerase-associated polypeptides (P1, P2, P3), hemagglutinin (HA), nucleoprotein (NP), neuraminidase (NA), membrane polypeptide (M), and a nonstructural polypeptide (NS). The molecular weights of these polypeptides correlate closely with the molecular weights of the eight genome RNA species found in fowl plague virus. The three high molecular weight polypeptides, P1, P2, and P3, were detected both in virions and infected cells, and their separate identity established by a two-dimensional tryptic peptide mapping procedure. An active RNA polymerase enzyme complex isolated from virions and virus-infected cells contained all three P proteins together with the NP protein. The nonstructural polypeptide (NS), together with the P proteins and the NP, appeared early in the infectious cycle, while the M protein and HA protein appeared later in infection. The NS and M polypeptides, which have similar molecular weights, were separated on SDS-polyacrylamide gels and shown to be distinct by tryptic peptide mapping.
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