The halotolerant carbonic anhydrase (dCAII) shares much with Carbonic Anhydrases (CA), generally, dCAII's unusual ability to weather extreme environments, notwithstanding.
dCAII has the , such as:
orange: two prominent alpha helixes (here, the two longest helixes)
green: 10 beta sheets
yellow: catalytic zinc
dCAII has, too, the CA's architectural elements.
pink: Catalytic zinc coordinating residues
red: substrate binding
purple: hydrogen binding
light-blue:acetate
Still, dCAII has a decidedly unusual to function in extremely high salt concentrations, but, also, in low salt concentrations.This balance comes from a predominantly negative surface, on the one hand, that is still less negative than that observed in halophiles, on the other hand. Therein lies the difference between Halophile and Halotolerant.
In summary, dCAII has all the properties of CA, and strikes the balance between positive to negative surface residues, which leads to tolerance of extremely salty conditions, and an ability to function in low salt conditions, as well.
