LasX, a transcriptional regulator of the lactocin S biosynthetic genes in Lactobacillus sakei L45, acts both as an activator and a repressor

• Published in: Biochimie 2002-05, Vol.84 (5), p.559-567
• Main Authors: Rawlinson, Elizabeth L.Andersen, Nes, Ingolf F., Skaugen, Morten
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - biosynthesis; ANTIMICROBIAL PROPERTIES; BACTERIOCINAS; BACTERIOCINE; BACTERIOCINS; Escherichia coli; EXPRESION GENICA; EXPRESSION DES GENES; GENE EXPRESSION; Gene Expression Regulation, Bacterial; Genetic Vectors; Lactobacillus - metabolism; LACTOBACILLUS SAKE; Lactobacillus sakei; Lantibiotic; Molecular Probes; PEPTIDE; PEPTIDES; PEPTIDOS; Promoter Regions, Genetic; PROPIEDADES ANTIMICROBIANAS; PROPRIETE ANTIMICROBIENNE; PROTEINAS; PROTEINE; PROTEINS; Regulation; Transcription Factors - metabolism; Transcriptional activator; Transcriptional repressor
• ISSN: 0300-9084; 1638-6183
• DOI: 10.1016/S0300-9084(02)01420-7

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.