Atypical melanosomal proteins in human malignant melanoma

Isolated melanosomes from human malignant melanoma lesions and normal tissues were solubilized with Triton X-100, and proteins were fractionated by polyacrylamide gel electrophoresis. Determination of the relative mobilities of protein bands at different acrylamide gel concentrations allowed the calculation of the molecular size and charge of melanosomal proteins. Three classes of proteins were demonstrable as follows: (a) those found only in melanoma; (b) those found only in normal melanosomes; and (c) proteins common to malignant and control tissues. The similarity of human melanoma protein banding patterns to those previously described in B-16 murine melanoma reaffirms the importance of the latter as a biochemical model for human studies; in addition, the presence of unique proteins in malignant tissue paralleled reports of aberrant polypeptides in organells of several other tumor systems.