Forms a portal in the viral capsid through which viral DNA is translocated during DNA packaging. Assembles as a dodecamer at a single fivefold axe of the T=16 icosahedric capsid. Binds to the molecular motor that translocates the viral DNA, termed terminase. Homododecamerizes. Interacts with terminase subunits TRM1 and TRM3. Belongs to the herpesviridae portal protein family.