Isoform G2P plays an essential role in viral DNA replication. Binds the origin of replication and cleaves the dsDNA replicative form I (RFI) and becomes covalently bound to it via phosphotyrosine bond, generating the dsDNA replicative form II (RFII). In turn, viral DNA replication initiates at the 3'-OH of the cleavage site. After one round of rolling circle synthesis, protein G2P is linked to the newly synthesized ssDNA and joins the ends of the displaced strand to generate a circular single-stranded molecule ready to be packed into a virion. Isoform G10P protein binds to double-stranded DNA and prevents hydrolysis by nucleases. Additionally, G10P is an inhibitor of DNA replication and may have a role in the transition from semiconservative replicative form DNA replication to single-stranded DNA synthesis in the life cycle. ATP + (deoxyribonucleotide)n-3'-hydroxyl + 5'-phospho-(deoxyribonucleotide)m = (deoxyribonucleotide)n+m + AMP + diphosphate. Belongs to the inovirus G2P protein family.