Some properties of coat proteins of two comoviruses

Properties of coat proteins of red clover mottle virus (RCMV) and broad bean strain virus (BBSV) belonging to comoviruses were studied using polyacrylamide gel electrophoresis in the presence of SDS (SDS-PAGE), proteolytic cleavage. Western blot analysis and monoclonal antibodies (MoAbs). Boiling in the absence of detergent did not cause disintegration of virus particles, but the latter occurred in the presence of 0.2% SDS. With 1% SDS the disintegration began at 50 degrees C and above 60 degrees C the virus particles were completely disintegrated. The relative molecular weights of the coat proteins as determined by SDS-PAGE method were 37.5 K and 20.5 K for RCMV, and 36.5 K and 22 K for BBCV, respectively. A spontaneous shortening of both coat proteins by proteolytic cleavage occurred in vitro. After cleavage with V8-protease the larger proteins gave 5 and 6 products, respectively (2 and 3 of them being the products of incomplete or nonspecific cleavage), the smaller proteins 4 products. The epitopes distinguished by 7 MoAbs were localized on only two V8-digest products of the larger coat proteins, but no MoAb binding to the smaller coat protein was observed.