Crystallization and peptide maps of neuraminidase “heads” from H2N2 and H3N2 influenza virus strains

Neuraminidase “heads” of two H2N2 influenza virus strains (A/Nederlands/68 and A/Korea/68) and one H3N2 strain (A/Hong Kong/68) were isolated by pronase digestion of recombinant viruses possessing neuraminidase molecules from these strains and H (NWS) hemagglutinin. The neuraminidase heads were purified and crystallized by dialysis against distilled water. Large flat crystals, which differed in appearance between the three strains, were obtained. Tryptic peptide maps of the crystallized neuraminidase heads of the Nederlands/68 and Hong Kong/68 strains were almost identical, suggesting that a virus closely related to the Nederlands/68 (H2N2) strain may have been the source of the neuraminidase for the formation of the H3N2 Hong Kong subtype.