Fig. 1

CA activity of COG4337 proteins. a Schematic images of Bn86287 and all2909 proteins. b Sequence alignment of COG4337 domains extracted from Bn86287 and all2909. Amino acids conserved in all and three of the four domains are shaded in black and gray, respectively. Positions of α-helices and β-strands estimated by X-ray crystallography are shown above the alignment. c–e CO₂ hydration activity of Bn86287, all2909, and α-class bovine CA (BCA) under various conditions: +EDTA, proteins were treated with 50 mM EDTA and 6 M urea; +PDA, proteins were treated with 50 mM 2,6-pyridinedicarboxylic acid (PDA); chemical symbols, metal ions were added to protein solution; I⁻, 1 mM KI was added to the reaction solution as an inhibitor. Bovine serum albumin (BSA) was used as a negative control. Significant differences compared to non-treated samples were determined by the two-tailed Student’s t test (*P < 0.02, **P < 0.01). In the graphs, error bars represent the SD calculated from three individual experiments. f HCO₃ dehydration activity of COG4337 proteins and BCA