Plays a critical role during packaging of viral DNA into empty capsids, where they are thought to be part of the packaging motor complex. The single stranded genomic DNA is packaged in a 3' to 5' direction and requires the association between viral DNA and Rep40. Regulates host PKA activity by interacting with host PRKX as a mechanism to interfere with helper virus propagation and to promote its own replication. Homooligomer. Interacts with host PRKX.