Soluble melanoprotein of tumor origin.

The procedure for isolating soluble melanoprotein from human malignant melanoma was described. Electron microscopy confirmed the absence of any contaminating organized particles. The melanoprotein was brown hygroscopic substance with 8.8% of melanin, easily soluble in water. The solution revealed general absorption with a shoulder at 280 nm. Chemical composition was typical for a melanoprotein complex with characteristic high sulphur content (2.1%) and abundance in zinc (210 mug Zn/g dry sample). Sedimentation and electrophoretic properties indicated relative homogeneity. Similar substance could also be isolated from Harding-Passey mouse melanoma. Such soluble melanoproteins have been needed for their broad exploitation in tumor immunology.