This model represents one of several distantly related families of phage portal protein. This protein forms a hole, or portal, that enables DNA passage during packaging and ejection. It also forms the junction between the phage head (capsid) and the tail proteins. It functions as a dodecamer of a single polypeptide of average mol. wt. of 40-90 KDa. [Mobile and extrachromosomal element functions, Prophage functions]