PLASMIDS OF THE PT181 FAMILY SHOW REPLICATION-SPECIFIC INITIATOR PROTEIN MODIFICATION

The rolling circle plasmids of Staphylococcus aureus regulate their re plication by controlling initiator (Rep) protein synthesis. It was dem onstrated recently that the pT181 initiator protein RepC is inactivate d during pT181 replication by the addition of an oligodeoxynucleotide, giving rise to a new form, RepC (A. Rasooly and R. P. Novick, Scienc e, 262:1048-1050). We establish here that this initiator modification occurs with four other members of the pT181 family and that it occurs in Bacillus subtilis as well as S. aureus. These results suggest that Rep conversion to Rep is probably universal among plasmids of the pT1 81 family and is not host dependent.