[Effect of the inter- and intramolecular disulfide bonds on the electrophoretic properties of influenza virus proteins].

The influence of disulphide bonds on the electrophoretic patterns of proteins of various influenza virus strains was studied by one-dimensional and two-dimensional electrophoresis in polyacrylamide gel. A significant effect of inter- and intramolecular disulphide bonds in proteins on their electrophoretic mobility was revealed for some structural viral proteins. In particular, polypeptides of WSN virus neuraminidase after routine treatment of the preparations with sodium dodecylsulphate and heating at a high temperature are detected as homodimers. A small portion of hemagglutinin polypeptides of 5 influenza strains under study are found as trimers under nonreducing conditions. Some subunits of the cleaved hemagglutinin (HA1 and HA2 proteins) of the virus preparations tested are not bound to each other by disulphide bonds. The electrophoretic mobility of intact hemagglutinin under nonreducing conditions is significantly higher than after the destruction of disulphide bonds. This phenomenon appears to be associated with increased compactness of molecules in electrophoresis under nonreducing conditions. Some data indicate a possibility of spontaneous closing up and unlocking of intramolecular disulphide bonds in hemagglutinin. In electrophoresis under nonreducing conditions, nucleoprotein of various influenza viruses is detected as multiple electrophoretic forms of approximately similar mobilities. The possibility of the existence of chemically similar but structurally different forms of nucleoprotein in vivo is discussed. In all purified influenza virus preparations tested a low molecular protein, P12, was found.