Subunit exchange between human and dog prealbumins.

When human prealbumin is mixed with carb,mylated human prealbumin or dog prealbumin hybrid prealbumins containing subunits of both types are formed. Spontaneous hybrid formation was a slow process. By renaturation from 6 mol/l quanidine hydrochloride, hybrids, distributed according to random combination of subunits were formed. The hybrids were stable, had a molecular weight similar to their parent molecules and bound thyroxine and retinol-binding protein. Only the hybrids with human and dog prealbumins participated in thioldisulphide exchange reactions as their parent molecules. The ability of prealbumin to exchange subunits of low molecular weight may be the reason why prealbumin concentration in cerebrospinal fluid is higher than expected from its plasma concentration and molecular weight.