FIGURE 9.

Cross-coordination of different antibiotic biosynthesis by the pseudo GBL receptors. In S. venezuelae, the pseudo GBL receptor JadR2 directly represses the transcription of jadR1. The cluster-situated regulator JadR1 activates the biosynthesis of Jd by activating the transcription of biosynthetic structural genes. JadR1 also represses the production of Cm by binding to the promoter of the structural genes. Jd and Cm could directly bind to JadR2, leading to its dissociation from the jadR1 promoter. In S. coelicolor, the pseudo GBL receptor ScbR2 directly represses the transcription of kasO. The cluster-situated regulator KasO is an activator in a cryptic type I polyketide synthase (PKSI) gene cluster. ScbR2 could also regulate the production of Red and Act indirectly. ScbR2 did not bind the GBL molecule SCB1 but could bind Red and Act, leading to its dissociation from the kasO promoter. Different antibiotics produced in one strain may affect each other by these pseudo GBL receptors, which bind and respond to antibiotic signals to coordinate their biosynthesis.