Peracetylated Bovine Carbonic Anhydrase (BCA-Ac18) Is Kinetically More Stable than Native BCA to Sodium Dodecyl Sulfate

Abstract

Bovine carbonic anhydrase (BCA) and its derivative with all lysine groups acetylated (BCA-Ac₁₈) have different stabilities toward denaturation by sodium dodecyl sulfate (SDS). This difference is kinetic: BCA-Ac₁₈ denatures more slowly than BCA by several orders of magnitude over concentrations of SDS ranging from 2.5 to 10 mM. The rates of renaturation of BCA-Ac₁₈ are greater than those of BCA, when these proteins are allowed to refold from a denatured state ([SDS] = 10 mM) to a folded state ([SDS] = 0.1 to 1.5 mM). On renaturation, the yields of the correctly folded protein (either BCA or BCA-Ac₁₈) decrease with increasing concentration of SDS. At intermediate concentrations of SDS (from 0.7 to 2 mM for BCA, and from 1.5 to 2 mM for BCA-Ac₁₈), both unfolding and refolding of the proteins are too slow to be observed; an alternative processprobably aggregationcompetes with refolding of the denatured proteins at those intermediate concentrations. Because it is experimentally impractical to prove equilibrium, it is not possible to establish whether there is a difference in the thermodynamics of unfolding/refolding between BCA and BCA-Ac₁₈.