Mannosidase II and the 135-kDa Golgi-specific antigen recognized monoclonal antibody 53FC3 are the same dimeric protein

Abstract

Monoclonal antibodies are frequently used as organelle-specific markers without identifying the specific antigen recognized. We have purified the protein recognized by a Golgi-specific monoclonal antibody 53FC3 (Burke, B., Griffiths, G., Reggio, H., Louvard, D., and Warren, G. (1982) EMBO J. 1, 1621-1628). Peptide microsequencing suggested that this antigen is mannosidase II, which was confirmed by cross-immunoprecipitation with an anti-mannosidase II antibody and by precipitation of mannosidase activity with the monoclonal antibody. Mannosidase II was found to exist normally as a disulfide-linked dimer.