Nucleotide sequences of the PA and PB1 genes of B/Ann Arbor/1/66 virus: comparison with genes of B/Lee/40 and type A influenza viruses.

The complete sequences of the PA and PB1 genome RNA segments of B/Ann Arbor/1/66 virus have been determined. The PA vRNA is 2308 bases long. Its complementary RNA has a single open reading frame of 2187 bases, capable of encoding a PA protein of 726 amino acids with a molecular weight of 83,175 Da. The predicted PA polypeptide has an overall net charge of -7.5 at pH 7.0. The PB1 vRNA is 2369 bases long. Its complementary RNA has a single open reading frame of 2277 bases, capable of encoding a PB1 protein of 752 amino acids with a molecular weight of 84,332 Da. The predicted PB1 polypeptide has an overall net charge of +18.5 at pH 7.0. Sequence homology comparisons of the PA and PB1 polypeptides from B/Ann Arbor/1/66 virus to the PA and PB1 polypeptides of type A influenza virus reveal respective homologies of approximately 38 and 60%. This high cross-type homology (61%) was previously reported for the PB1 protein of B/Lee/40 virus (Kemdirim et al., 1986). The cross-type homology for the PA protein is similar to that of other non-polymerase proteins, but is substantially lower than that seen for the PB1 protein. Thus, the high cross-type homology that exists for the PB1 gene does not appear to be a characteristic of all polymerase genes.