INHIBITION OF SENDAI VIRUS HEMAGGLUTININ-NEURAMINIDASE BY THE FUSION PROTEIN

The Sendai virus envelope contains two glycoproteins: the fusion (F) p rotein and the hemaggiutinin-neuraminidase (HN). Inactivation of F cau ses the loss of fusogenic activity and an increase of the neuraminidas e activity of HN. After inactivation of F, HN can be inhibited by fetu in or asialofetuin, as already observed on the water-soluble, C-termin al fragment of HN (Dallocchio, F., Bellini, T., Martuscelli, G., Baioc chi, M., and Tomasi, M. (1991) Biochem. Int. 25, 663-668). Disruption of viral envelopes by detergents does not affect the neuraminidase act ivity of virions contaning inactive F, while it causes an increase of the neuraminidase activity in native virions. Reconstitution of HN int o liposomes is accompanied by a decrease of enzymatic activity, due to the random inside-outside distribution of the protein. However, the d ecrease of the neuraminidase activity is higher in liposomes contianig both HN and F. These data suggest that F inhibits the neuraminidase a ctivity of HN. (C) 1994 Academic Press, Inc.