A thylakoid-located carbonic anhydrase regulates CO2 uptake in the cyanobacterium Synechocystis sp. PCC 6803 (New Phytol)

The cyanobacterial CO₂ concentrating mechanism (CCM) is dependent on a continuous supply of inorganic carbon (Ci) to rubisco inside carboxysomes in order to function optimally.  CO₂ uptake pathways are therefore of great importance for a full understanding of the cyanobacterial CCM.  Sun et al demonstrate that a thylakoid bound carbonic anhydrase (CA), EcaB, converts CO₂ to bicarbonate (HCO₃^–) as part of both NDH-1 complexes.  This beta-CA was shown to bind to the NDH-1 complexes through interaction with CupA and CupB.  The precise function of EcaB has yet to be determined due to conflicting pieces of evidence, and it is not conserved across the cyanobacterial lineage.  However, its responsiveness to high illumination and CO₂ do suggest an important contribution to CO₂ uptake.  (Summary by Mike Page) New Phytol 10.1111/nph.15575