ATP-dependent DNA helicase and primase essential for viral DNA replication and recombination (PubMed:21606333, PubMed:22977246, PubMed:32009150). 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 (PubMed:21606333, PubMed:22977246, PubMed:32009150). ATP or dTTP hydrolysis propels each helicase domain to translocate 2 nt per step sequentially along DNA (PubMed:30679383, PubMed:17604719). Mediates strand transfer when a joint molecule is available and participates in recombinational DNA repair through its role in strand exchange (PubMed:9096333, PubMed:8617248). 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 (PubMed:6454135, PubMed:9139692). ATP + H2O = ADP + H(+) + phosphate Binds 2 Mg(2+), one of which is catalytic. Homohexamer (PubMed:16777142, PubMed:10880454, PubMed:30679383, PubMed:10535735, PubMed:10892646, PubMed:14636571). Assembles as a hexamer onto linear or circular ssDNA in the presence of ATP or dTTP (PubMed:10880454). Present in a mixture of heptamers and hexamers in the absence of DNA (PubMed:16777142, PubMed:14636571). Interacts (via C-terminus) with the viral DNA polymerase that is bound to DNA; this interaction is essential to initiate leading-strand DNA synthesis (PubMed:15795374, PubMed:22977246, PubMed:23675753, PubMed:26620561). The priming complex consists of 2 DNA polymerases and 1 helicase-primase hexamer that assemble on the DNA template (PubMed:23675753). Interacts with the single-stranded DNA-binding protein (PubMed:1634539). Part of the replicase complex that includes the DNA polymerase, thioredoxin, the primase/helicase and the single-stranded DNA binding protein (PubMed:22977246). Isoform 4A contains the primase/helicase region, whereas isoform 4B contains only the helicase region (PubMed:7310871). Isoform 4A and 4B are present in a molar ratio of 1:8 (PubMed:2829184). The N-terminus zinc finger domain is essential for delivering the primed DNA template to the DNA polymerase (PubMed:12769857, PubMed:10200256). The central core domain contains the primase activity (PubMed:2829184). The C-terminus region is responsible for the helicase activity and binds 1 Mg(2+)-dTTP (PubMed:2829184, PubMed:9185573, PubMed:30679383). Belongs to the Teseptimavirus DNA helicase/primase family.