Isoform G1P plays an essential role in phage assembly. It is required to increase the number of adhesion zones between the inner and outer membranes of the host cell. The extrusion of neo-synthesized phages occurs at these adhesion sites. May be involved with G4P in creating zone through which the phage assembled and extruded (By similarity). Isoform G11P is also involved in phage assembly, probably playing a structural role in the formation of the phage assembly site. Interacts with G4P; this interaction results in a complex that spans the inner an outer host membranes. Belongs to the inovirus G1P protein family.