[The purification of the protein alternative to alfa-fetoprotein]

The subject of the study was the unidentified protein Ag A2/3, which is found in some cells of rat hepatoma McA RH7777 and their clones. The feature of this protein is that its expression is alternative to alfa-fetoprotein (AFP), i.e. Ag A2/3 is not found in cells and cell clones containing AFP, and vice versa. Ag A2/3 proved to be a cell stress protein--it was induced by heavy metal salts (Pb2+ and Cd2+) in the liver of adult rats and AFP+/A2/3(-) clones of hepatomas; the attenuation of AFP synthesis occurred simultaneously. This paper describes the preparation of Ag A2/3 for sequence analysis, and the scheme of Ag A2/3 purification. When trying to obtain a blot for sequencing it proved to be impossible to reveal the protein using McAb to Ag A2/3 after the transfer of separated proteins on PVDF. The reactivity of the antigen determinant was reestablished with blot processing on PVDF membrane with methanol and Twin 80.