title: Involvement of CarA/LitR and CRP/FNR family transcriptional regulators in light-induced carotenoid production in Thermus thermophilus.
abstract: Members of the CarA/LitR family are MerR-type transcriptional regulators that contain a C-terminal cobalamin-binding domain. They are thought to be involved in light-induced transcriptional regulation in a wide variety of nonphototrophic bacteria. Based on the distribution of this kind of regulator, the current study examined carotenoid production in Thermus thermophilus, and it was found to occur in a light-induced manner. litR and carotenoid and cobalamin biosynthesis genes were all located on the large plasmid of this organism. litR or cobalamin biosynthesis gene knockout mutants were unable to switch off carotenoid production under dark conditions, while a mutant with a mutation in the downstream gene adjacent to litR (TT_P0055), which encodes a CRP/FNR family transcriptional regulator, was unable to produce carotenoids, irrespective of light conditions. Overall, genetic and biochemical evidence indicates that LitR is bound by cobalamin and associates with the intergenic promoter region between litR and crtB (phytoene synthase gene), repressing the bidirectional transcription of litR and crtB. It is probable that derepression of LitR caused by some photodependent mechanism induces the expression of TT_P0055 protein, which serves as a transcriptional activator for the crtB operon and hence causes the expression of carotenoid biosynthesis and the DNA repair system under light condition.
authors.affiliation: Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Takano
authors.forename: Masato
authors.initials: M
authors.lastname: Kondo
authors.forename: Noriyoshi
authors.initials: N
authors.lastname: Usui
authors.forename: Toshimitsu
authors.initials: T
authors.lastname: Usui
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Ohzeki
authors.forename: Ryuta
authors.initials: R
authors.lastname: Yamazaki
authors.forename: Misato
authors.initials: M
authors.lastname: Washioka
authors.forename: Akira
authors.initials: A
authors.lastname: Nakamura
authors.forename: Takayuki
authors.initials: T
authors.lastname: Hoshino
authors.forename: Wataru
authors.initials: W
authors.lastname: Hakamata
authors.forename: Teruhiko
authors.initials: T
authors.lastname: Beppu
authors.forename: Kenji
authors.initials: K
authors.lastname: Ueda
mesh_terms: D002338:Carotenoids / Q000096:biosynthesis*; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008027:Light; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016963:Thermus thermophilus / Q000235:genetics* / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D004269:DNA, Bacterial; D014157:Transcription Factors; D002338:Carotenoids