The inactivated plasmid inititator protein RepC/RepC* may have a regulatory role.

During replication of the plasmid pT181, the initiator protein RepC is modified by the addition of an oligodeoxynucleotide, giving rise to a new form, RepC*. Here we show that during in vitro replication, RepC* is radioactively labeled, suggesting that the source of the RepC* oligodeoxynucleotide is the newly synthesized pT181 DNA. The RepC/RepC* heterodimer retains its ability to bind the pT181 double-strand origin and, therefore, it may act as a competitive inhibitor of the RepC homodimer during replication.