Influence of the C terminus of the small protein subunit of bean pod mottle virus on the antigenicity of the virus determined using monoclonal antibodies and anti-peptide antiserum.

Middle component particles of bean pod mottle virus (BPMV) containing small protein subunits with a cleaved C terminus were used to produce monoclonal antibodies (MAbs). All MAbs were specific for cryptotopes, i.e. epitopes present only on dissociated BPMV protein. The MAbs reacted more strongly with virus protein preparations containing the cleaved form of the small subunit than with preparations containing only the uncleaved form. It seems that the presence of additional residues at the C terminus of the intact small subunit interferes with antibody binding. Antibodies raised against synthetic peptides corresponding to the C terminus of the uncleaved small subunit reacted with both intact virions and dissociated subunits. This C-terminal region seems to play a dominant role in the antigenicity of the virus.