Fig. 3

Schematic representation of the locus for Gassericin E (GasE) production (a) and detailed analysis of DNA sequences of putative promoters and Rho-independent terminators (b, c, d, e, f). a P1, P2, P3a and P3b are putative promoter sequences, and T1 is a putative Rho-independent transcription terminator. Genes encoding Gassericin E (gaeA), the putative complement peptide GaeX (gaeX) and their putative immunity protein (gaeI), could form an transcriptional unit, driven by two putative alternative promoters (P3a and P3b). Genes encoding the three-component regulatory system formed by the autoinducer peptide (gaeP), the histidine protein kinase (gaeK) and the response regulator (gaeR), as well as the ABC-transporter (gaeT) and the accessory protein (gaeC), seem to form one transcriptional unit; however two different transcripts could be formed, one larger driven by promoter P1 involving gaePKRTC and one shorter driven by promoter P2 involving gaeTC. a, b, c, d The putative promoters P1, P2, P3a and P3b were detected with the Neural Network Promoter Prediction online server [30], with a promoter score cut-off of 0.9 (score are shown in brackets). The typical -35 and -10 boxes and the ribosome binding sites (RBS) are shown; the +1 indicates the putative transcription start. Putative regulatory DNA sequences (Direct L- and R- repeats) are in italics. e Rho-independent terminator; base-pairs are in boldface and apical loop in italics. f Alignment of the direct DNA repeats (L and R) found upstream of the GasE and GaeP putative promoters (P1 and P3b) and the consensus L- and R- repeats involved in quorum-sensing regulation of Blp bacteriocins in Streptococcus thermophilus [34]