Serum IgG-like glycoferroprotein: identification of its final dissociation form of thermostable protein coupled with albumin.

Human serum IgG-like glycoferroprotein identical to ascitic IgG-like glycoferroprotein that binds labeled monoclonal antibodies to CA125 is a complex consisting of three proteins: IgG, human serum albumin, and unidentified thermostable protein. Final dissociation form of serum IgG-like glycoferroprotein also appears as a complex of three nonidentical polypeptides with a molecular weight of 55 kDa (PC55) migrating in the albumin zone of thermostable protein coupled with albumin and structures chemically identical to human serum albumin and IgG heavy chains. Under denaturing conditions of electrophoresis in polyacrylamide gel, IgG-like glycoferroprotein and PC55 have the same molecular weight (about 55 kDa), while under reducing conditions their weight is about 75 kDa. Transition form (form the lower to the higher molecular weight) appears as an oblique (at about ≈ 30°) protein band creating a ladder string effect. Ladder string effect was reproduced with thermostable protein coupled with albumin, PC55, IgG-like glycoferroprotein, with all commercially available human and bovine albumins, rat albumin as well as with heated and renatured albumins and can serve as electrophoretic identification sign for thermostable protein coupled with albumin. Renatured after boiling (100°C for 15 min) bovine albumin under reducing conditions appeared as bow string twisted in helix, that raises molecule in 2.5 turns from ≈ 2 to ≈ 75 kDa. These data attest to the existence of an albumin double and to its possible double structure.