Figure 8.

Model of pTP interactions during replication initiation. (A) A parental (p)TP molecule stays covalently bound to the 5′ end of the Ad genome (lines) after having primed the preceding replication round. The observed cooperative binding to short DNA duplexes could mimic the interaction of an incoming priming pTP with the parental (p)TP (arrow). The ds/ssDNA binding region of pTP is indicated by hatching. (B) The ssDNA binding affinity of pTP could contribute to pTP/pol binding stability on an unwound origin structure, while the pTP region providing the priming Ser580 should present the Ser hydroxyl group to the catalytic center (black circle) in the Ad DNA pol. Potential stabilizing contacts can be made with the parental (p)TP (arrow) and two ssDNA contact points spaced by the dimensions of pTP: the displaced strand (bound in the DNA binding region) and the three 3′ terminal nucleotides of the template strand (3′).