Forms the portal vertex of the capsid (PubMed:10801350) (PubMed:19744688, PubMed:21570409). This portal plays critical roles in head assembly, genome packaging, neck/tail attachment, and genome ejection (By similarity). The portal protein multimerizes as a single ring-shaped homododecamer arranged around a central channel (PubMed:11812138, PubMed:21570409). Binds to the 6 packaging RNA molecules (pRNA) forming a double-ring structure which in turn binds to the ATPase gp16 hexamer, forming the active DNA-translocating motor (PubMed:15886394, PubMed:11130079). This complex is essential for the specificity of packaging from the left DNA end. Homododecamer (PubMed:11130079, PubMed:11526317) (PubMed:11812138). Interacts (via N-terminus) with the pRNA (PubMed:15886394). Present in 12 copies in the virion. Belongs to the phi29likevirus portal protein family.