A 2 (N2) Neuraminidase of the X-7 Influenza Virus Recombinant: Determination of Molecular Size and Subunit Composition of the Active Unit

Abstract

Neuraminidase activity of influenza virus was directly seen on sodium dodecyl sulfate polyacrylamide gels with the aid of the synthetic substrate, methoxyphenol neuraminic acid. Neuraminidase (NA) appeared as a high-molecular-weight fraction with a size in the range of 220,000 to 250,000 daltons. Isolation of this fraction from the X-7 strain of influenza virus, dissociation with sodium dodecyl sulfate, and reduction showed the presence of two polypeptides of 66,000 (NA 1 ) and 58,000 (NA 2 ) molecular weights in equimolar concentration. We postulate that the minimum active unit for the viral A 2 neuraminidase is a tetramer composed of two NA 1 and two NA 2 subunits.