Location, size, and complexity of epitopes on the coat protein of beet necrotic yellow vein virus studied by means of synthetic overlapping peptides

Five regions on the coat protein of BNYVV which had been shown previously to be involved in the formation of continuous epitopes were further analyzed by means of synthetic overlapping peptides. It was found that at least some of these regions may encompass several overlapping epitopes (or parts thereof). Four monoclonal antibodies (MAbs) which were known to be specific for the C-terminus of BNYVV coat protein (amino acids 182-188 = RTSPPGQ) were found to react with different sets of peptides which had either the sequence RTS, RTSP, RTSPP, or PPGQ in common. Two other MAbs which also had been shown previously to be specific for the C-terminus of BNYVV coat protein failed to react with overlapping decapeptides. Two epitopes which were previously located in the areas of amino acids 115-125 and 125-140 could now be located more precisely on the sequences SANVRRD (amino acids 115-121) and AESSG (amino acids 128-132), respectively. Replacement studies with alanine showed that not all amino acids within these sequences are equally important for antibody binding. On the other hand, amino acids outside these sequences may strongly influence the reactivity of epitopes. The accessibility of amino acid sequences on the particles of BNYVV is discussed.