ATP-dependent DNA helicase and primase essential for viral DNA replication and recombination. The helicase moves 5' -> 3' on the lagging strand template, unwinding the DNA duplex ahead of the leading strand polymerase at the replication fork and generating ssDNA for both leading and lagging strand synthesis. ATP or dTTP hydrolysis propels each helicase domain to translocate sequentially along DNA. Mediates strand transfer when a joint molecule is available and participates in recombinational DNA repair through its role in strand exchange. Primase activity synthesizes short RNA primers at the sequence 5'-GTC-3' on the lagging strand that the polymerase elongates using dNTPs and providing the primase is still present. ATP + H2O = ADP + H(+) + phosphate Binds 2 Mg(2+), one of which is catalytic. Homohexamer. Assembles as a hexamer onto linear or circular ssDNA in the presence of ATP or dTTP. Interacts (via C-terminus) with the viral DNA polymerase that is bound to DNA; this interaction is essential to initiate leading-strand DNA synthesis. The priming complex consists of 2 DNA polymerases and 1 helicase-primase hexamer that assemble on the DNA template. Interacts with the single-stranded DNA-binding protein. Part of the replicase complex that includes the DNA polymerase, the primase/helicase and the single-stranded DNA binding protein. Isoform 4A contains the primase/helicase region, whereas isoform 4B contains only the helicase region. The N-terminus zinc finger domain is essential for delivering the primed DNA template to the DNA polymerase. The central core domain contains the primase activity. The C-terminus region is responsible for the helicase activity and binds 1 Mg(2+)-dTTP. Belongs to the Teseptimavirus DNA helicase/primase family.