Trimerization of the reovirus cell attachment protein (σI) induces conformational changes in σI necessary for its cell-binding function

The implications of reovirus σI protein trimerization on its cell-binding function were investigated. Both monomeric and trimeric forms of σI were found to be present when full-length type 3 reovirus SI transcripts prepared in vitro were translated in rabbit reticulocyte lysates. Pulse-chase experiments demonstrated that monomers were precursors of trimers. However, only the trimeric form was capable of binding to cell surface receptors. Protease and antibody recognition analyses revealed significant structural differences between these two σI forms at both the N- and C-termini. Our results suggest that trimerization of protein of is accompanied by extensive conformational changes necessary for its cell attachment function.