Plays a role in packaging a single copy of genome into the prohead. The terminase is composed of two subunits (a large and a small) and the small subunit recognizes the DNA to be encapsidated. Once the DNA is packaged, the terminase detaches from the connector and the tail replaces it to finish maturation of the virion. Homooctamer (Probable). Interacts with the terminase large subunit gp19; the active complex is probably heterooligomeric. Belongs to the terminase small subunit family.