Identification of a plasma membrane protein that specifically binds bleomycin.

In this paper, the association of radiolabelled bleomycin on the plasma membrane of DC-3F cells is shown to be saturable, displaying classical features of a ligand-receptor binding. This association corresponds to the presence of 140,000 to 400,000 binding sites at the surface of the cells with a half-saturating concentration of 5 microM. Moreover, using a gel electrophoresis procedure to separate membrane proteins incubated with radiolabelled bleomycin, we demonstrate the existence of a membrane protein of about 250kDa able to specifically bind bleomycin. This membrane bleomycin-binding protein could play a major part in the association of bleomycin with the cells and in its further internalization, a process that has not been elucidated yet.