
%0 Journal Article
%A Omata, Tatsuo 
%A Takahashi, Yukari 
%A Yamaguchi, Osamu 
%A Nishimura, Takashi 
%T Structure, function and regulation of the cyanobacterial high-affinity bicarbonate transporter, BCT1
%J Functional Plant Biology
%D 2002/03/19
%V 29
%N 3
%P 151-159
%K ABC transporter, bicarbonate transporter, CO2 concentrating mechanism, cyanobacteria.
%R https://doi.org/10.1071/PP01215
%U https://www.publish.csiro.au/paper/PP01215 
%X The cmpABCD operon of the cyanobacterium Synechococcus sp. strain PCC7942, which is transcribed specifically under CO2-limited growth conditions, encodes an ATP-binding cassette (ABC) transporter involved in HCO3&#8211;uptake (designated BCT1). The product of the cmpA gene is a 42-kDa protein anchored to the plasma membrane, which binds HCO3&#8211; with high affinity (Kd= 5 &#181;M) and acts as the substrate-binding protein of the transporter. The apparent Km(HCO3&#8211;) of BCT1 is 15 &#181;M. BCT1 has the highest affinity for HCO3&#8211; among the HCO3&#8211; transporters of the Synechococcus strain and is essential for competitive utilization of HCO3&#8211; under CO2-limited conditions. BCT1 is closely related to the cyanobacterial nitrate/nitrite transporter (NRT) encoded by the nrtABCD genes. The BCT1 and NRT transporters, together with the putative cyanate transporter of cyanobacteria, comprise a monoanion transporter subfamily in the family of ABC importers. BCT1 and NRT are present in most fresh-water strains of cyanobacteria but seem to be absent in marine cyanobacterial strains. The low CO2-responsive induction of thecmp operon requires a LysR family protein CmpR, which is similar to CbbR (RbcR), the activator of the CO2 fixation operons of chemoautotrophic and purple photosynthetic bacteria. 
