GENETIC-ANALYSIS OF THE REPLICATION REGION OF THE LACTOBACILLUS PLASMID VECTOR PPSC22

The sequence and genetic organization of the 1,600-bp replication regi on of the Lactobacillus vector pPSC22, a plasmid derived from a 7-kb c ryptic plasmid of L. plantarum used for the cloning of heterologous ge nes in several lactobacilli, were determined. Sequence analysis reveal ed the presence of a plus origin of replication containing the two fun ctional elements nic and bind, required for initiation of the leading strands typical of the rolling circle (RC)-replicating plasmids belong ing to the pLS1 family. Two open reading frames (copA and repA) were l ocated within the Lactobacillus portion of pPSC22. The repA gene produ ct, a 234-amino acid protein, showed homologies with the Rep protein o f the streptococcal plasmid pLS1 and contained the three conserved dom ains detected in most Rep proteins of RC-replicating plasmids and ss-c oliphages. The genetic organization of the replication region of pPSC2 2 shared relevant homologies with the lactococcal plasmids pWVO1 and p FX2.