SEQUENCE AND STRUCTURE ALIGNMENT OF PARAMYXOVIRUS HEMAGGLUTININ-NEURAMINIDASE WITH INFLUENZA-VIRUS NEURAMINIDASE

A model is proposed for the three-dimensional structure of the paramyx ovirus hemagglutinin-neuraminidase (HN) protein. The model is broadly similar to the structure of the influenza virus neuraminidase and is b ased on the identification of invariant amino acids among HN sequences which have counterparts in the enzyme-active center of influenza viru s neuraminidase. The influenza virus enzyme-active site is constructed from strain-invariant functional and framework residues, but in this model of HN, it is primarily the functional residues, i.e., those that make direct contact with the substrate sialic acid, which have identi cal counterparts in neuraminidase. The framework residues of the activ e site are different in HN and in neuraminidase and appear to be less strictly conserved within HN sequences than within neuraminidase seque nces.