The Phage Portal Protein (PPP) Subclass forms the portal vertex of the capsid (Olia et al. 2011). This portal plays critical roles in head assembly, genome packaging, neck/tail attachment, and genome ejection (Motwani and Teschke 2019). Procapsid assembly may initiate with a nucleation complex composed of portal and scaffolding proteins (Motwani and Teschke 2019). The portal protein multimerizes as a single ring-shaped homododecamer arranged around a central channel. Switches upon genome packaging from an asymmetrical conformation in the procapsid (PC-portal) to a symmetrical ring in the mature capsid (MV-portal). This change of conformation may serve as a signal for headful packaging (Lokareddy et al. 2017).