Regeneration of Enzyme Activity by Air Oxidation of Reduced Subtilisin-Modified Ribonuclease

Fully reduced bovine ribonuclease, a molecule which probably exists in a random coil configuration (1, 2)) will, under the influence of molecular oxygen alone, oxidize to form an organized, enzymatically active product in high yield (3, 4). This material seems indistinguishable on the basis of physical properties from native ribonuclease (RNase) . These observations suggest that the information determining not only the covalent structure, but also the secondary and tertiary structure of the molecule, is contained in the amino acid sequence itself. It is of interest to determine which portions of the sequence are most necessary for correct refolding. The reduction and subsequent oxidation of subtilisin-modified RNasei has, therefore, been studied in an attempt to obtain at least a partial answer to this question. The results described below indicate that after removal of 20 of the 124 residues which form the RNase chain, an enzymatically active product may be produced by oxidation of the fully reduced derivative.