Forms the portal vertex of the capsid. 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 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. This complex is essential for the specificity of packaging from the left DNA end. Homododecamer. Interacts (via N-terminus) with the pRNA. Present in 12 copies in the virion. Belongs to the phi29likevirus portal protein family.