Involved in the replication of viral DNA (PubMed:9858710). It is required at the very beginning of the virus amplification, conditions in which a low number of viral DNA molecules enter the host cell, possibly to recruit the limiting amount of initiation factors at the replication origins (PubMed:9858710). Once the infection process is established and the other replication proteins reach optimal concentration, it becomes dispensable (PubMed:9858710). Optimizes the binding of protein p6 at the viral DNA ends, thus favoring the initiation of replication (PubMed:12480935). Homodimer. Interacts with the histone-like protein p6; this interaction optimizes the binding of protein p6 at the viral DNA ends, thus favoring the initiation of replication. Expressed in the early phase of the viral replicative cycle (PubMed:6274853). The C2 promoter controls protein p17 transcription and is strongly inhibited by the viral histone-like protein p6, probably because of the formation of a p6-DNA nucleoprotein complex at the right end of the viral genome. Thus, protein p17 is synthesized very early after infection, and its synthesis declines later on due to the inhibition of the C2 promoter by protein p6. Belongs to the phi29likevirus protein p56 family.