Forms the portal vertex of the capsid (PubMed:2685327, PubMed:24126213). This portal plays critical roles in head assembly, genome packaging, neck/tail attachment, and genome ejection. The portal protein multimerizes as a single ring-shaped homododecamer arranged around a central channel. Binds to the terminase subunits to form the packaging machine. Attaches to the host inner membrane most likely through interaction with host yidC and forms together with chaperone gp40 an initiator complex to form the prohead. Homododecamer. Interacts with the large terminase subunit. Interacts with the major capsid protein. Interacts with the capsid vertex protein. Located at a unique 5-fold vertex of the icosahedral capsid. Localization at the inner host membrane is likely due to interactions with host membrane proteins such as yidC. Belongs to the Tevenvirinae portal protein family.