title: LasX, a transcriptional regulator of the lactocin S biosynthetic genes in Lactobacillus sakei L45, acts both as an activator and a repressor.
abstract: The 11 kb las locus, present on the 50 kb plasmid pCIM1, specifies the production of the lantibiotic lactocin S in Lactobacillus sakei L45. The gene cluster is organized into two oppositely orientated operons, lasAMNTUVPJW (lasA-W) and lasXY, the former of which contains the biosynthetic, immunity and transport genes. We have previously shown that inactivation of lasX abolishes lactocin S production and causes a drastic reduction in lasA-specific transcripts (encoding pre-lactocin S). The aim of this study was to determine whether or not the product of lasX, which is significantly similar to Rgg-like regulators, was directly involved in transcriptional regulation of the lactocin S biosynthetic genes. The divergently orientated and overlapping promoters, P(lasA)(-W) and P(lasXY), were transcriptionally fused to the Escherichia coli gusA gene, and the activity of the fusions was assayed in the presence and absence of lasX, which was expressed on a separate plasmid. A significant stimulation of expression (5-6-fold) of the P(lasA-W)-gusA fusion was observed in the presence of lasX, whereas expression of the P(lasXY)-gusA construct was reduced 1.5-2-fold. Our results strongly suggest that LasX is a bifunctional regulatory protein, acting both as an activator of lasA-W transcription and as a repressor of lasXY transcription. While a transcription stimulation activity has been described for several of the Rgg-like proteins, the present study is the first to report an autorepressor function for a member of this protein group.
authors.affiliation: Laboratory of Microbial Gene Technology, P O Box 5051, Agricultural University of Norway, N-1432 As, Norway. elizabeth.andersen@ikb.nlh.no
authors.forename: Elizabeth L Andersen
authors.initials: EL
authors.lastname: Rawlinson
authors.forename: Ingolf F
authors.initials: IF
authors.lastname: Nes
authors.forename: Morten
authors.initials: M
authors.lastname: Skaugen
mesh_terms: D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D001430:Bacteriocins; D015964:Gene Expression Regulation, Bacterial; D005822:Genetic Vectors; D007778:Lactobacillus / Q000378:metabolism*; D015335:Molecular Probes; D010455:Peptides; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001430:Bacteriocins; D015335:Molecular Probes; D010455:Peptides; D014157:Transcription Factors; C103925:lactocin S