title: Vitamin B12 regulates photosystem gene expression via the CrtJ antirepressor AerR in Rhodobacter capsulatus.
abstract: The tetrapyrroles haem, bacteriochlorophyll and cobalamin (B12 ) exhibit a complex interrelationship regarding their synthesis. In this study, we demonstrate that AerR functions as an antirepressor of the tetrapyrrole regulator CrtJ. We show that purified AerR contains B12 that is bound to a conserved histidine (His145) in AerR. The interaction of AerR to CrtJ was further demonstrated in vitro by pull down experiments using AerR as bait and quantified using microscale thermophoresis. DNase I DNA footprint assays show that AerR containing B12 inhibits CrtJ binding to the bchC promoter. We further show that bchC expression is greatly repressed in a B12 auxotroph of Rhodobacter capsulatus and that B12 regulation of gene expression is mediated by AerR's ability to function as an antirepressor of CrtJ. This study thus provides a mechanism for how the essential tetrapyrrole, cobalamin controls the synthesis of bacteriochlorophyll, an essential component of the photosystem.
authors: Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, 47405, USA.
authors: Zhuo
authors: Z
authors: Cheng
authors: Keran
authors: K
authors: Li
authors: Loubna A
authors: LA
authors: Hammad
authors: Jonathan A
authors: JA
authors: Karty
authors: Carl E
authors: CE
authors: Bauer
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001429:Bacteriochlorophylls / Q000096:biosynthesis*; D002498:Centrifugation; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D012097:Repressor Proteins / Q000378:metabolism*; D016354:Rhodobacter capsulatus / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014805:Vitamin B 12 / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; C107183:CrtJ protein, Rhodobacter; D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D014805:Vitamin B 12