Molecular analysis of the gene cluster involved in the production and secretion of enterocins 1071A and 1071B and of the genes responsible for the replication and transfer of plasmid pEF1071

Plasmid pEF1071 (9328 bp), bearing the structural genes of enterocins 1071A and 1071B, had been sequenced and nine genes were identified. The genes responsible for the production and transfer of enterocins 1071A and 1071B are arranged in two operons. The first operon (EntABI) contains the genes ent1071A, ent1071B and entI that encodes enterocin 1071A, enterocin 1071B and immunity to these bacteriocins, respectively. The second operon (EntTD) contains two genes, viz. abc (also named entT) and entD, encoding a putative ABC transporter (697 aa) and an accessory protein (697 aa), respectively. Three genes (mobC, mobA and mobX), situated downstream of the second operon, encode proteins of 127, 346 and 224 amino acids, respectively, and are presumably involved in the mobilization of plasmid pEF1071. The ninth gene was identified as a putative repA gene encoding a protein of 327 amino acids. The transcription initiation sites of the genes ent1071A, abc, mobA, mobX and repA were determined by primer extension. By inserting the cat gene into the ent1071B gene, and thereby disrupting the operon structure, we have shown that bacteriocins Ent1071A and Ent1071B act independently against target bacteria.