Role and Function of LitR, an Adenosyl B12-Bound Light-Sensitive Regulator of Bacillus megaterium QM B1551, in Regulation of Carotenoid Production.
The LitR/CarH family of proteins is a light-sensitive MerR family of transcriptional regulators that contain an adenosyl B12 (coenzyme B12 or AdoB12)-binding domain at the C terminus. The genes encoding these proteins are found in phylogenetically diverse bacterial genera; however, the biochemical properties of these proteins from Gram-positive bacteria remain poorly understood. We performed genetic and biochemical analyses of a homolog of the LitR protein from Bacillus megaterium QM B1551, a Gram-positive endospore-forming soil bacterium. Carotenoid production was induced by illumination in this bacterium. In vivo analysis demonstrated that LitR plays a central role in light-inducible carotenoid production and serves as a negative regulator of the light-inducible transcription of crt and litR itself. Biochemical evidence showed that LitR in complex with AdoB12 binds to the promoter regions of litR and the crt operon in a light-sensitive manner. In vitro transcription experiments demonstrated that AdoB12-LitR inhibited the specific transcription of the crt promoter generated by a σ(A)-containing RNA polymerase holoenzyme under dark conditions. Collectively, these data indicate that the AdoB12-LitR complex serves as a photoreceptor with DNA-binding activity in B. megaterium QM B1551 and that its function as a transcriptional repressor is fundamental to the light-induced carotenoid production.


OBJECTIVE
Members of the LitR/CarH family are AdoB12-based photosensors involved in light-inducible carotenoid production in nonphototrophic Gram-negative bacteria. Our study revealed that Bacillus LitR in complex with AdoB12 also serves as a transcriptional regulator with a photosensory function, which indicates that the LitR/CarH family is generally involved in the light-inducible carotenoid production of nonphototrophic bacteria.
Life Science Research Center, College of Bioresource Sciences, Nihon University, Kanagawa, Japan takano.hideaki@nihon-u.ac.jp.
Hideaki
H
Takano
Life Science Research Center, College of Bioresource Sciences, Nihon University, Kanagawa, Japan.
Kou
K
Mise
Life Science Research Center, College of Bioresource Sciences, Nihon University, Kanagawa, Japan.
Kenta
K
Hagiwara
Life Science Research Center, College of Bioresource Sciences, Nihon University, Kanagawa, Japan.
Naoya
N
Hirata
Life Science Research Center, College of Bioresource Sciences, Nihon University, Kanagawa, Japan.
Shoko
S
Watanabe
Life Science Research Center, College of Bioresource Sciences, Nihon University, Kanagawa, Japan.
Minami
M
Toriyabe
Life Science Research Center, College of Bioresource Sciences, Nihon University, Kanagawa, Japan.
Hatsumi
H
Shiratori-Takano
Life Science Research Center, College of Bioresource Sciences, Nihon University, Kanagawa, Japan.
Kenji
K
Ueda
D000595:Amino Acid Sequence; D001410:Bacillus megaterium / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002338:Carotenoids / Q000378:metabolism*; D003038:Cobamides / Q000737:chemistry / Q000378:metabolism*; D018983:DNA Footprinting; D003850:Deoxyribonuclease I / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D008027:Light; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding
D001426:Bacterial Proteins; D003038:Cobamides; D002338:Carotenoids; D003850:Deoxyribonuclease I; C000913:cobamamide