THE KINETICS OF FORMATION OF NATIVE RIBONUCLEASE DURING OXIDATION OF THE REDUCED POLYPEPTIDE CHAIN

Open Access
Publisher Website
Google Scholar
Abstract
Chemical and physical studies on bovine RNase seem to indicate the manner of correct pairing of half-cystine residues and to present evidence for the assumption of the native secondary and tertiary structures in the amino acid sequence itself. Optical rotation and spectral studies were also carried out on the native protein which suggest that some of the SS bonds formed during the early stage of oxidation are not identical with those of the native protein but undergo rearrangement to yield the native configuration. The most striking phenomenon observed is the marked lag phase before enzyme activity appears, during which time the SH titer and specific optical rotation change along a curve similar to that of a first order reaction. During the formation of native RNase from the reduced chain, SH groups might be converted to SS bonds by one of two general mechanisms, the first involving the initial pairing of the correct half cystine residues and the second, of random pairing with subsequent reshuffling to yield the native arrangement It is tentatively concluded that oxidation of SH groups in this system occurs initially through random formation of SS bonds with subsequent rearrangement taking place under the influence of SS interchange driven by thermodynamic forces toward the most probable form, native RNase.