title: Mechanism of low CO2-induced activation of the cmp bicarbonate transporter operon by a LysR family protein in the cyanobacterium Synechococcus elongatus strain PCC 7942.
abstract: The cmp operon of the cyanobacterium Synechococcus elongatus strain PCC 7942, encoding the subunits of the ABC-type bicarbonate transporter, is activated under CO2-limited growth conditions in a manner dependent on CmpR, a LysR family transcription factor of CbbR subfamily. The 0.7 kb long regulatory region of the operon carried a single promoter, which responded to CO2 limitation. Using the luxAB reporter system, three cis-acting elements involved in the low-CO2 activation of transcription, each consisting of a pair of LysR recognition signatures overlapping at their ends, were identified in the regulatory region. CmpR was shown to bind to the regulatory region, yielding several DNA-protein complexes in gel shift assays. Addition of ribulose-1,5-bisphosphate (> 1 mM) or 2-phosphoglycolate (> 10 microM) enhanced the binding of CmpR in a concentration-dependent manner, promoting formation of large DNA-protein complexes. Given the involvement of O2 in adaptive responses of cyanobacteria to low-CO2 conditions, our results suggest that 2-phosphoglycolate, which is produced by oxygenation by ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) of ribulose-1,5-bisphosphate under CO2-limited conditions, acts as the co-inducer in the activation of the cmp operon by CmpR.
authors.affiliation: Laboratory of Molecular Plant Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa, Nagoya 464-8601, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nishimura
authors.forename: Yukari
authors.initials: Y
authors.lastname: Takahashi
authors.forename: Osamu
authors.initials: O
authors.lastname: Yamaguchi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Suzuki
authors.forename: Shin-Ichi
authors.initials: S
authors.lastname: Maeda
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Omata
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D001639:Bicarbonates / Q000378:metabolism*; D002245:Carbon Dioxide / Q000494:pharmacology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005988:Glyceric Acids / Q000494:pharmacology; D008969:Molecular Sequence Data; D009876:Operon / Q000235:genetics*; D011485:Protein Binding / Q000187:drug effects; D046940:Synechococcus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D001639:Bicarbonates; D004268:DNA-Binding Proteins; D005988:Glyceric Acids; C422911:cmpR protein, Synechococcus; D002245:Carbon Dioxide; C008885:2-phosphoglycerate