Denaturation of bovine carbonic anhydrase B by guanidine hydrochloride. A process involving separable sequential conformational transitions.

The denaturation and renaturation of bovine carbonic anhydrase B is a thermodynamically reversible process, uncomplicated by aggregation or disuhide bond formation. The reaction is less cooperative than is the unfolding and refolding of most globular proteins, in that distinct successive stages can be observed both in equilibrium and kinetic measurements. This enzyme is therefore ideally suited for investigation of the mechanism of folding of an unfolded polypeptide chain. As part of this work the properties of the native enzyme have been carefully reinvestigated. A somewhat smaller molecular weight (29,000) and sedimentation coefficient (&u = 2.89 S) than previously reported were obtained. The absence of cystine or cysteine has been unambiguously established.