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 process-probably aggregation-competes 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.