Self assembles to form a helical capsid wrapping up the viral genomic DNA. The capsid displays a filamentous structure with a length of 760-1950 nm and a width of 6-8 nm. The virion assembly and budding take place at the host inner membrane. Homomultimerizes. There are about 2,700 copies of this protein in the phage capsid. Insertion into the host inner membrane requires YidC but not the Sec translocon. Virion assembly occurs after insertion. Belongs to the inovirus capsid protein family.