jadR3, encoding a deduced γ-butyrolactone receptor, is a barX homologue.Disruption of jadR3 greatly decreased the production of jadomycin and chloramphenicol.Gel retardation assays and DNase I footprinting experiments revealed that JadR3 could specifically bind to the promoter regions of jadR1, jadR2, jadW1 and jadR3.A consensus sequence is found in these binding sites, similar to the authentic γ-butyrolactone receptors.