Characterization of a monoclonal antibody recognizing a DAG-containing epitope conserved in aphid transmissible potyviruses: evidence that the DAG motif is in a defined conformation

Two viral proteins, the helper component-protease and the coat protein, are required for the non-persistent aphid transmission of potyviruses. In the potyvirus coat protein, the tripeptide aspartate–alanine–glycine (DAG) has often been shown to be involved. A monoclonal antibody, raised against a synthetic decapeptide containing the DAG tripeptide, reacted with the peptide as well as with isolates of soybean mosaic, tobacco etch and tobacco vein mottling potyviruses. Experiments indicate that the monoclonal antibody recognizes a conformational rather than a sequential epitope. The data support the suggestion that the DAG region plays a structural role to determine a coat protein-helper component-protease conformation that influences aphid transmission.