May initiate with G9P the virion concomitant assembly-budding process, by interacting with the packaging signal of the viral genome. The assembly-budding takes place at the host inner membrane. In turn, G7P and G9P are present at the end of the filamentous virion that emerges first from the bacterial host. Prior to assembly, is found associated with the bacterial host inner membrane. There are about five copies of this protein per mature phage that are located on the tail side of the filamentous virion with G9P (By similarity). Belongs to the inovirus G7P protein family.