Proteolytic activation of the haemagglutinin-neuraminidase of Newcastle disease virus involves loss of a glycopeptide.

The uncleaved (HN0) and the cleaved (HN) forms of the haemagglutinin-neuraminidase glycoprotein of Newcastle disease virus (NDV), strain Ulster, were analysed by polyacrylamide gel electrophoresis under reducing and non-reducing conditions. When HN0 is converted into HN, a glycopeptide with an apparent mol. wt. of about 8000, which is not found in the mature spike, is removed.