Purification of a glycoprotein from mouse ascites fluid by immunoaffinity chromatography which is related to the major glycoprotein of murine leukemia viruses. Immunologic and structural comparison with purified viral glycoproteins.

Proteins immunologically related to the major glycoprotein from murine leukemia viruses, gp70, are expressed in the tissue and body fluids of unmanipulated mice in the absence of virus particle production. Cross-reactive gp70 was isolated from ascites fluid of NZB and (NZB X NZW)F1 mice utilizing immunoaffinity chromatography. An enriched antibody preparation bound to Sepharose was used as an immunosorbent to purify gp70 over 600-fold in one step with a 30% recovery. The gp70s from ascites fluid were compared with gp70s purified from laboratory virus strains Friend, Rauscher, Moloney, and Scripps leukemia viruses. Direct antibody binding studies showed that the viral gp70s were more closely related to each other than to the gp70s from ascites fluid. Furthermore, the gp70s from ascites fluid were more reactive with antibody to xenotropic virus than were the gp70s from the laboratory viruses tested. Tryptic peptide map analysis of radioiodinated proteins showed that gp70 from Scripps virus is closely related to gp70 from Moloney virus in primary structure and less closely related structurally to gp70 from Rauscher virus and gp70 from NZB ascites fluid.