Sequence determination of the Sendai virus HN gene and its comparison to the influenza virus glycoproteins

The nucleotide sequence of the Sendai virus (SV) HN (hemagglutinin-neuraminidase) gene was determined. The deduced primary structure of the protein showed only one hydrophobic domain likely to represent the transmembrane region, but at its N terminus. Since the SV F protein is anchored in the membrane at its C terminus, the two SV glycoproteins are thus membrane-anchored in opposite orientations, similar to the two influenza virus (FLU) glycoproteins. Amino acid sequence comparisons of the SV HN and the FLU HA and NA proteins revealed homologies between 100 amino acids of the hemagglutinin region of the FLU HA protein and the C terminus of the SV HN, and between 200 amino acids of the neuraminidase region of the FLU NA and the central region of SV HN. Alignment of the neuraminidase, hemagglutinin, and fusion regions shared by these glycoproteins suggest the structure of a possible ancestral gene.