Localization of the Herpesvirus Portal

Herpes simplex virus type 1 (HSV-1) contains a large double-stranded DNA genome of about 152,000 base pairs, which requires accommodation in a correspondingly massive particle. In the nucleus, viral DNA is packaged into a spherical precursor particle called the procapsid via the portal protein, pUL6, which occupies one of the procapsid's twelve vertices. Upon DNA insertion, the procapsid matures into an angular, icosahedral capsid and undergoes the subsequent steps in the viral life cycle. While the overall structure of the viral portal has been known for some time [1, 2], its exact orientation and position in the context of the capsid have been controversial. Investigations have been hampered by the fact that the one portal-bearing vertex is practically visually indistinguishable from the other eleven vertices. This has led to various publications, using different technical approaches, placing the portal both inside the particle as well as in line with other capsomers and in various orientations