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Mechanism of low CO 2 ‐induced activation of the cmp bicarbonate transporter operon by a LysR family protein in the cyanobacterium Synechococcus elongatus strain PCC 7942
Author(s) -
Nishimura Takashi,
Takahashi Yukari,
Yamaguchi Osamu,
Suzuki Hiroshi,
Maeda Shinichi,
Omata Tatsuo
Publication year - 2008
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2008.06137.x
Subject(s) - operon , biology , synechococcus , ribulose , rubisco , biochemistry , transcription (linguistics) , cyanobacteria , oxygenase , promoter , atp binding cassette transporter , transcription factor , gene , genetics , transporter , bacteria , gene expression , escherichia coli , linguistics , philosophy
Summary The cmp operon of the cyanobacterium Synechococcus elongatus strain PCC 7942, encoding the subunits of the ABC‐type bicarbonate transporter, is activated under CO 2 ‐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 CO 2 limitation. Using the luxAB reporter system, three cis ‐acting elements involved in the low‐CO 2 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 μM) enhanced the binding of CmpR in a concentration‐dependent manner, promoting formation of large DNA–protein complexes. Given the involvement of O 2 in adaptive responses of cyanobacteria to low‐CO 2 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 CO 2 ‐limited conditions, acts as the co‐inducer in the activation of the cmp operon by CmpR.