ATPase required for the genome encapsidation reaction. Part of the active packaging motor via the binding to the packaging RNA (pRNA), itself fixed to the head-tail connector at the unique portal vertex of the prohead. Binds and supercoils the DNA-gp3 to produce an initiation complex for DNA packaging. Provides the energy to actively pump the viral DNA into the prohead. Approximately one molecule of ATP is used in the packaging of 2 bp of viral DNA. After packaging, the ATPase and the pRNA are released from the prohead. ATP + H2O = ADP + H(+) + phosphate Homohexamer. Interacts with the packaging RNA. Part of a DNA-gp3-gp16 complex. Belongs to the phi29likevirus gp16 family.