Participates in the transport of viral genome to neighboring plant cells directly through plasmodesmata, without any budding. TGBp2 and TGBp3 are necessary for intracellular delivery of TGBp1-containing vRNPs to plasmodesmata. Can gate plasmodesmata and increase their size exclusion limit. Induces host actin cytoskeleton network thickening, which probably plays a major role in virus cell-to-cell movement. Interacts with movement proteins TGB1 and TGB2. TGB1-TGB3-TGB2 complex formation is enhanced by ATP hydrolysis. Probably localizes to plasmodesmata-associated membrane compartments called peripheral membrane bodies (PMBs). Associates with host actin filaments. The 2nd transmembrane domain is involved in plasmodesmata targeting. Belongs to the virgaviridae TGB3 movement protein family.