title: Genetic control for light-induced carotenoid production in non-phototrophic bacteria.
abstract: Carotenoids are naturally occurring yellow or orange pigments that serve as a protectant against photo-oxidative damages. Among the wide variety of producers, the prokaryotes generate a broad spectrum of carotenoids with diverse chemical structures that are expected to have a high potential in biotechnological applications. Bacterial carotenogenesis occurs in a constitutive or light-induced manner, which suggests the diversity of the regulatory mechanism. The mechanism for light-induced carotenoid production in non-phototrophic bacteria has been studied in detail in Myxococcus xanthus, a Gram-negative gliding bacterium. The complicated mechanism involves the activation of an extracytoplasmic function (ECF) sigma factor (CarQ), which leads to the sequestration of a MerR family transcriptional regulator (CarA) that represses the expression of the carotenoid biosynthesis genes in the dark. Recently, we identified another regulatory mechanism for light-induced carotenogenesis in Streptomyces coelicolor A3(2), a Gram-positive soil bacterium. In this organism, the transcription of the carotenoid biosynthesis gene cluster is specified by LitS, a photo-inducible ECF sigma factor. The evidence indicates that the photo-dependent transcription of litS is mediated by LitR, a MerR family transcriptional regulator. In addition, it is suggested that the conformational alteration of LitR upon receiving the illumination signal determines its binding to DNA. The carboxy-terminal domain of LitR contains a possible binding site for Vitamin B12, which may serve as a capturing apparatus for the illumination signal.
authors.affiliation: Life Science Research Center, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa, 252-8510, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Takano
authors.forename: Dalal
authors.initials: D
authors.lastname: Asker
authors.forename: Teruhiko
authors.initials: T
authors.lastname: Beppu
authors.forename: Kenji
authors.initials: K
authors.lastname: Ueda
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002338:Carotenoids / Q000096:biosynthesis*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008027:Light; D016941:Myxococcus xanthus / Q000235:genetics / Q000378:metabolism*; D013302:Streptomyces / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C051124:MerR protein, Bacteria; D002338:Carotenoids