Membrane compartmentalization of melanosomal gp75.

A melanosomal integral membrane glycoprotein of 75 kD (gp75) has been previously identified as the human homologue of the product specified by the murine brown locus. We presently report that this molecule may be susceptible to limited proteolysis and extrinsic radioiodination in intact, live cells. Consequently, it is suggested that its cellular location might include the plasma membrane and/or a cellular compartment easily accessible to proteases and to chemically catalyzed vectorial iodination. This is of interest in view of the potential applicative value of gp75 as a target for the radioimmunoscintography of melanoma lesions.