THE 36K POLYPEPTIDE SYNTHESIZED IN NEWCASTLE-DISEASE VIRUS-INFECTED CELLS POSSESSES PROPERTIES PREDICTED FOR THE HYPOTHESIZED V-PROTEIN

Newcastle disease virus (NDV) virions posses two proteins which react strongly with monoclonal antibody 688 following separation by high resolution two-dimensional (isoelectric focusing/SDS) PAGE and detection by Western blotting. One is the phosphorylated nucleocapsid-associated 53K [P (NAP)] protein, the other comigrates with the 36K protein detected by radiolabelling NDV-infected chick embryo fibroblasts. [S-35]Cysteine/[H-3]leucine dual-labelling experiments show that the 36K protein is very rich in cysteine compared to the P (NAP) protein. In the Beaudette C strain it comigrates on one-dimensional SDS-polyacrylamide gels with the matrix protein (M); however, it is resolved from the slower migrating M protein from the Ulster strain of NDV. The size, strain-specific isoelectric point, high cysteine content and antigenic relatedness to the P (NAP) protein suggest that the 36K protein is the 'V' protein of NDV, the counterpart of which is found in other Paramyxoviridae.