Sequence of the neuraminidase gene of an avian influenza A virus (A/parrot/ulster/73, H7N1).

The complete sequence of the neuraminidase (NA) gene of the influenza A strain A/parrot/ Ulster /73 ( H7N1 ) has been determined after reverse transcribing and cloning it into the pBR322 plasmid, followed by subcloning into M13 vectors and sequencing with dideoxynucleotide chain terminators. The gene consists of 1458 nucleotides and codes for a protein of 469 amino acids. The neuraminidase has seven potential glycosylation sites. According to the molecular weight as determined by electrophoretic migration in polyacrylamide gel all of these sites might carry a carbohydrate side chain. When the parrot Ulster NA was compared with two other N1 neuraminidases, those of the human PR8 and WSN strains, deletions in the stalk region of 15 amino acids for PR8 NA and of 16 amino acids for WSN NA were apparent. No further rearrangements were found within N1 neuraminidases. Although the parrot Ulster strain was isolated 40 years after the two human strains, the base sequence homology of their NA genes is still 83 or 82%, respectively.