[Self-aggregation of the structural protein encoded by rice ragged stunt Oryzavirus genome segment 8]

Rice ragged stunt oryzavirus (RRSV) is a member of the genus oryzavirus within the family Reoviridae. Its genome consists of ten segments of dsRNA. The functions of all products encoded by these viral genome segments, except one encoded by S9, have not yet been elucidated. In the present study, the ORF of S 8 of RRSV-Philippines isolate was sequenced and expressed in E. coli. The 67 kD product of S8 could be self-cleaved into two fragments with molecular weights of 43 kD and 26 kD. Western blotting indicated that both 67 kD and 43 kD products were major structural proteins of the virus. It was also found that the 67 kD protein could self aggregate into aggregates with higher sedimentation rate in sucrose gradients during centrifugation. Moreover, the self-aggregation process could be accelerated by the complex of S6 product and genome dsRNAs of RRSV. These results suggest that the S8 products, 67 kD or 43 kD, may be the structural components of the viral inner-capsid.