Figure 1.
Map of the purple membrane regulon and carotenoid biosynthesis pathway. (a) A map for the chromosomal locus coding for bop, brp, bat, blp, and crtB1 genes. The site for ISH1 insertion in bat in strain SD20 is indicated. The four mapped promoters, Pbop, Pbrp, Pblp, and PcrtB1, are indicated with bent arrows either above or below the map. (b) The pathway for carotenoid biosynthesis. Steps 1 and 2 in bacteria are catalyzed by the crtB1 gene product: phytoene synthase; steps 3 and 4 in plants are catalyzed by phytoene desaturase (Pds); and step 5 in Halobacterium sp. is catalyzed by Brp.