A melanoma cell surface laminin binding protein with apparent m_r 90, 000

Laminin promotes adhesion of various cell types via multiple interactions with cell surface components. We have used a laminin domain involved in adhesion of melanoma cells, peptide F9 (Charonis et at., J. Cell Biol. 107:1253 [1988]), to examine its specific interaction with cell surface components. Cells were surface labeled, solubilized, and the cell surface associated macromolecules were purified via laminin and F9 affinity columns. We have observed that a macromocule with apparent molecular weight 90, 000 interacts with laminin and peptide F9. This macromolecule does not change electrophoretic mobility upon reduction, cannot be removed from the cell surface by high salt treatment and partitions in the detergent phase of Triton X-114. These results suggest that this macromolecule is associated with melanoma cell surfaces and may be involved in their interaction with laminin.