A complex role for the γ‐butyrolactone SCB1 in regulating antibiotic production in Streptomyces coelicolor A3(2)

Abstract

Many streptomycetes produce extracellular γ‐butyrolactones. In several cases, these have been shown to act as signals for the onset of antibiotic production. Synthesis of these molecules appears to require a member of the AfsA family of proteins (AfsA is required for A‐factor synthesis of the γ‐butyrolactone A‐factor and consequently for streptomycin production in Streptomyces griseus). An afsA homologue, scbA, was identified in Streptomyces coelicolor A3(2) and was found to lie adjacent to a divergently transcribed gene, scbR, which encodes a γ‐butyrolactone binding protein. Gel retardation assays and DNase I footprinting studies revealed DNA binding sites for ScbR at − 4 to − 33 nt with respect to the scbA transcriptional start site, and at − 42 to − 68 nt with respect to the scbR transcriptional start site. Addition of the γ‐butyrolactone SCB1 of S. coelicolor resulted in loss of the DNA‐binding ability of ScbR. A scbA mutant produced no γ‐butyrolactones, yet overproduced two antibiotics, actinorhodin (Act) and undecylprodigiosin (Red), whereas a deletion mutant of scbR also failed to make γ‐butyrolactones and showed delayed Red production. These phenotypes differ markedly from those expected by analogy with the S. griseus A‐factor system. Furthermore, transcription of scbR increased, and that of scbA was abolished, in an scbR mutant, indicating that ScbR represses its own expression while activating that of scbA. In the scbA mutant, expression of both genes was greatly reduced. Addition of SCB1 to the scbA mutant induced transcription of scbR, but did not restore scbA expression, indicating that the deficiency in scbA transcription in the scbA mutant is not solely due to the inability to produce SCB1, and that ScbA is a positive autoregulator in addition to being required for γ‐butyrolactone production. Overall, these results indicate a complex mechanism for γ‐butyrolactone‐mediated regulation of antibiotic biosynthesis in S. coelicolor.

2-Alkyl-4-hydroxymethylfuran-3-carboxylic acids, antibiotic production inducers discovered by Streptomyces coelicolor genome mining

“…SCB1 (compound 2) (Fig. 1 A), the most studied of these GBLs, appears to function mainly in the transcriptional regulation of a gene cluster proposed to direct production of an unknown polyketide metabolite (7,(11)(12)(13)(14). The S. coelicolor chromosome contains 1 homologue of afsA called scbA, which is located adjacent to the cryptic modular polyketide synthase gene cluster (13) and is required for the biosynthesis of GBLs (15).…”

PREDetector: A new tool to identify regulatory elements in bacterial genomes

“…Estimation of the reliability of the predictions: determination of the appropriate cut-off score. The cis-acting sequences bound by ScbR of Streptomyces coelicolor [6,7] were used as training set to generate the scbR weight matrix. (A) Prediction reliability output: fractions of sites located either within intergenic or coding regions in S. avermitilis.…”

“…In addition, with PREDetector users have also access to sites located within coding regions and regions in between two translation Stop codons and therefore generally omitted during investigations because systematically considered with no functional elements. The characteristics and the possibilities offered to users by PREDetector are explained and illustrated below with the prediction of the ScbR (c-butyrolactone binding protein) regulon of Streptomyces avermitilis using experimentally validated ScbR binding sites of Streptomyces coelicolor [6,7].…”

Angucyclines as signals modulate the behaviors of Streptomyces coelicolor

“…AdpA is the master regulator of differentiation and secondary metabolism that coordinates the expression of hundreds of genes involved in aerial hyphae production and sporulation (23)(24)(25). scbA and scbR (encoding GBL receptor and synthase, respectively) form a divergent gene pair controlling the temporal production of GBL signal in S. coelicolor (33). Both redD and kasO are cluster-situated regulatory genes, controlling production of Red and the yellow-colored coelimycin, respectively (21,26).…”