The surface membrane properties of murine 3T3, malignant SV40-transformed 3T3 and revertant variants of transformed cells (revertants have regained several behavioral properties characteristic of normal cells growing in tissue culture) are being examined with attention focused on substrate-attached material (SAM), cell-substratum adhesion sites which remain bound to the tissue culture substrate after EGTA-mediated detachment of cells. SAM is greatly enriched in the cell surface glycoprotein fibronectin and certain glycosaminoglycan-containing proteoglycans. Preliminary experiments indicate that two different proteoglycan aggregates in SAM may bind to fibronectin in different ways to act as positive or negative effectors of adhesion. We will seek evidence that fibronectin in these adhesion sites can bind to various GAG-containing species in dissociated SAM and will examine the specificity and topology of this binding in SAM from the three cell types grown under various physiological conditions. Evidence also will be sought that fibronectin:proteoglycan complexes exist as "native" components in these adhesion sites. These studies will shed further light on how these two classes of cell surface components effect adhesion of normal or malignant cells to extracellular matrices in the first place, how detachment of cells to generate "footprints" during motility of cells is effected by one type of supramolecular proteoglycan aggregate and, finally, how normal, malignant cells may differ in their adhesive processes.