Antibody as an immunological probe for studying the refolding of bovine serum albumin. An immunochemical approach to the identification of possible nucleation sites.

Specifically purified antibody to either domain I, domain III, or to subregions of domains I or III of serum albumin was added to refolding mixtures containing reduced serum albumin but no other refolding catalyst. It was found that the refolding of reduced albumin was greatly enhanced by the presence of specific antibody in the refolding mixture, that this enhancement was restricted to that domain for which the added antibody was directed, and that antibody-mediated enhancement of refolding in the NH2-terminal portion of each domain was delayed as compared to that seen in the COOH-terminal portion of each domain. Thus, an apparent COOH-terminal to NH2-terminal pathway of refolding within each domain was observed, which is consistent with the proposed evolutionary pathway of the albumin molecule and also consistent with the proposed presence of a nucleation center in the COOH-terminal double disulfide loop of each domain.