The bop Gene Cluster of Halobacterium halobium

Abstract

Summary The protein, bacterio-opsin, complexed with retinal functions as a light-driven proton pump in the purple membrane of the halophilic archaeon, Halobacterium halobium . The gene encoding bacterio-opsin ( bop ) is located within a cluster of genes, two of which are regulatory genes affecting bop gene expression. A third gene, blp , is co-regulated with the bop gene by low oxygen tension. Characterization of Bop mutants and transcriptional analyses of wild-type cultures grown under conditions of high light intensity and low oxygen tension have provided information about the roles of the two regulatory genes, brp and bat . A model has been proposed in which the Bat protein functions as an oxygen detector and trans -acting activator, whereas Brp is a membrane-bound light sensor. Moreover, conserved motifs located upstream of the bop gene most likely represent binding sites for regulatory factors mediating the response of the bop gene to high light intensity and low oxygen tension.