Conserved cysteine-including domains and arginine in cyanobacterial PRX from different subfamilies. A total of 42 sequences were used in the alignment of cyanobacterial PRX. Six samples were extracted to represent their own subfamilies. Shades with different colours indicate the distinct PRX subfamilies. Typical catalytic traits of PRX are indicated by the red box. The conserved arginines are indicated by yellow shading.