(A) Sc-1 cell binding to the 110-kD polypeptide after the addition of 110-kD or R-3Fn polypeptides. The dotted line indicates cell adhesion in the absence of competing polypeptide. Inhibition resulting from 110 kD, R-3Fn7-9, R-3Fn9-10, R-3Fn10, R-3Fn6-10SPSDN, and R-3Fn8/10D are significantly different. (B) Sc-1 cell adhesion to immobilized recombinant polypeptides in the presence or absence of anti-integrin antibodies at their optimal blocking concentrations. The amount of R-3Fn polypeptide coated onto plastic, or added in solution, was not in molar equivalents, because it is well known that the biological activity of such fragments is rather low3,11 23 and must be compensated for by using an excess of added protein. Fragments were therefore used at concentrations up to 100 μg/mL, based on independent dose-dependency tests, which established that the fragments were not significantly more active above the indicated concentrations. Antibody inhibition assays reported here do not include immobilized 110 kD, R-3Fn9, or R-3Fn4-6.
