Bacteriophage portal proteins form a dodecamer and is located at a five-fold vertex of the viral capsid. The portal complex forms a channel through which the viral DNA is packaged into the capsid, and exits during infection. The portal protein is though to rotate during DNA packaging [1]. Portal proteins from different phage show little sequence homology, so this family does not represent all portal proteins.

1: DNA packaging: a new class of molecular motors. Moore SD, Prevelige PE Jr; Curr Biol 2002;12:96-98. PMID:11839289