LIGHT-INDUCED CAROTENOGENESIS IN MYXOCOCCUS-XANTHUS - DNA-SEQUENCE ANALYSIS OF THE CARR REGION

The carR region encodes a light-inducible promoter, a negative regulat or of the promoter and a trans-acting activator that controls the ligh t-inducible Myxococcus xanthus carotenoid biosynthesis regulon. DNA se quence analysis revealed, downstream of the promoter, three translatio nally coupled genes, carQ, carR and carS. Sequencing of mutations demo nstrated that carR encoded the negative regulator and was an integral membrane protein. Mutant construction and sequencing revealed that car S was the trans-acting activator and that carQ was a positive regulato r of the promoter. Neither gene encodes proteins with known sequence-s pecific DNA-binding motifs. The sequence of the light-inducible promot er region, identified by primer extension analysis, showed similarity to the consensus sequence of the Escherichia coli stress response ('he at-shock') promoters.